BIOLOGY 
LIBRARY 


THE  MAIN  CURRENTS  OF 
ZOOLOGY 


BY 
WILLIAM  A.  LOCY,  PH.D.,  Sc.D. 

AUTHOR  OF  "  BIOLOGY  AND  ITS  MAKERS  " 
PROFESSOR  OF  ZOOLOGY  IN  NORTHWESTERN  UNIVERSITY 


NEW   YORK 

HENRY  HOLT  AND  COMPANY 
1918 


Copyright  1918, 

BY 
HENRY  HOLT  AND  COMPANY 


PREFACE 

THE  conviction  has  been  gradually  forced  upon  the 
writer  that  persons  who  wish  to  get  an  insight  into 
zoology  as  a  science  have  difficulties  in  finding  the 
necessary  helps.  The  conventional  treatise  on 
zoology  deals  chiefly  with  facts  about  animals  and 
certain  phenomena  of  their  lives,  but  omits  a  con- 
current account  of  the  results  of  zoological  advances. 
In  educational  institutions,  also,  the  method  of 
using  animal  types  as  the  sole  background  of  knowl- 
edge, together  with  drill  on  the  facts  observed  in  the 
laboratory,  has  resulted  in  a  one-sided  and  inad- 
equate conception  of  zoology. 

Zoological  progress  represents  a  stream  of 
thought — not  merely  accretions  of  knowledge  about 
animals.  In  order  to  comprehend  zoology  in  the 
light  of  its  progress  it  is  necessary  to  trace  its  main 
currents;  merely  to  accumulate  a  certain  set  of  facts 
about  animals  will  cause  one  ever  to  remain  outside 
of  the  subject.  It  is  well  to  remember  also  that  the 
interpretations  resulting  from  zoological  observa- 
tions have  had  great  influence  hi  liberating  thought 
and  on /general  intellectual  advancement. 

iii 

381031 


iv  PREFACE 

It  is  the  purpose  of  this  volume  to  attempt  to 
picture  zoology  as  a  unified  science.  There  are  ex- 
cellent books  that  supply  a  knowledge  of  the  animal 
kingdom — this  one  aims  to  add  some  knowledge  of  the 
science  itself.  It  is,  therefore,  intended  to  be  a  book 
of  collateral  reading  for  courses  in  practical  zoology, 
and,  while  written  with  this  primarily  in  mind,  it 
is,  at  the  same  time,  adapted  to  the  needs  of  the 
general  reader  who  wishes  to  become  familiar  with 
the  progress  of  zoology. 

In  the  preparation  of  the  material  I  have  been 
indebted  for  helpful  suggestions  to  my  colleagues, 
Professor  Sidney  I.  Kornhauser  and  Dr.  Olof  Larsell. 
I  am  also  indebted  to  the  Macmillan  Company  for 
permission  to  use  verbatim  a  considerable  portion 
of  my  article  "Zoology"  published  by  that  firm  in 
A  Cyclopaedia  of  Education,  1913. 

WILLIAM  A.  LOCY. 


CONTENTS 

CHAPTER  PAGE 

I.  ZOOLOGY  AS  A  SUBJECT  OF  GENERAL  EDUCATION — OUTLINE 

OP  THE  PROGRAM i 

II.  THE  OUTSTANDING  BIOLOGICAL  ADVANCES  OF  THE  NINE- 
TEENTH CENTURY 10 

The  Discovery  of  Protoplasm  and  its  Bearing  on  Bio- 
logical Progress n 

The  Formulation  of  the  Cell-Theory 16 

Establishment  of  the  Doctrine  of  Organic  Evolution  ...  22 

in.  THE  OUTSTANDING  BIOLOGICAL  ADVANCES — CONTINUED  ....  24 
The  Rise  of  Bacteriology  and  the  Demonstration  of  the 

Germ-Theory  of  Disease 25 

The  Experimental  Study  of  Heredity 34 

IV.  ZOOLOGY  EMERGES 43 

V.   LlNNJEUS  AND  HlS  INFLUENCE 52 

VI.  CUVIER  AND  STRUCTURAL  ZOOLOGY 62 

VII.  THE  RISE  OF  EMBRYOLOGY 70 

VHI.  GENERAL  PHYSIOLOGY  AS  A  DIVISION  OF  ZOOLOGY 77 

EX.  THE  ANIMAL  KINGDOM 84 

X.  ZOOLOGY  OF  FOSSIL  REMAINS 95 

XI.  MAIN  PATHWAYS  AND  RECENT  TENDENCIES  OF  ZOOLOGY  . . .  106 

XII.  A  CHAPTER  ON  INSECTS 125 

Xm.  THEORIES  OF  ORGANIC  EVOLUTION 143 

XIV.  SOME  MISCELLANEOUS  TOPICS 165 

Painless  Surgery 165 

Jenner  and  Vaccination 170 

XV.  THE  TEN  FOREMOST  MEN  OF  ZOOLOGICAL  HISTORY— NA- 
TIONAL CONTRIBUTIONS  TO  ZOOLOGICAL  PROGRESS — 
THE  RANK  OF  DIFFERENT  NATIONS  IN  BIOLOGICAL 

PROGRESS 174 

XVI.  SOME  USEFUL  BOOKS— A  SELECTED  READING-LIST  WITH 
BRIEF  COMMENTS  ON  THE  RELATIVE  MERITS  OF  BOOKS 
AND  PERIODICAL  ARTICLES  ON  ZOOLOGICAL  SUBJECTS  .  188 

INDEX 209 

v 


ILLUSTRATIONS 

FIG.  PAGE 

1.  FELIX  DUJARDIN 16 

2.  MAX  SCHULTZE 16 

3.  THEODOR  SCHWANN 16 

4.  THEODOR  BOVERI 16 

5.  CHARLES  DARWIN 22 

6.  Louis  PASTEUR 28 

7.  SIR  JOSEPH  LISTER 36 

8.  ROBERT  KOCH .'...,. ,.« 36 

9.  SIR  FRANCIS  GALTON 36 

10.  GREGOR  MENDEL 36 

11.  ARISTOTLE 54 

12.  CAROLUS  LINNAEUS 54 

13.  RUDOLPH  LEUCKART 54 

14.  GEORGES  CUVIER 54 

15.  ALBRECHT  VON  KOELLIKER 72 

16.  KARL  ERNST  VON  BAER 72 

17.  FRANCIS  M.  BALFOUR 72 

18.  CLAUDE  BERNARD 72 

19.  JOHANNES  MULLER 80 

20.  E.  D.  COPE 96 

21.  JOSEPH  LEIDY 96 

22.  CHARLES  SEDGWICK  MINOT 96 

23.  CHARLES  Ons  WHITMAN 96 

24.  Louis  AGASSIZ 118 

25.  J.  HENRI  FABRE 136 

26.  WALTER  REED 136 

27.  W.  T.  G.  MORTON 136 

28.  EDWARD  JENNER 136 

29.  J.  B.  LAMARCK 146 

30.  WILLIAM  HARVEY 156 

31.  THOMAS  H.  HUXLEY 156 

32.  AUGUST  WEISMANN 156 

33.  HUGO  DE  VRIES 156 

vii 


THE 
MAIN  CURRENTS  OF  ZOOLOGY 

CHAPTER  I 

ZOOLOGY  AS  A  SUBJECT  OF  GENERAL  EDUCA- 
TION.   OUTLINE  OF  THE  PROGRAM 

THERE  are  no  problems  of  greater  human  interest 
than  those  of  biology,  and  when  we  recognize  that 
zoology  is  the  central  subject  of  biology  it  imme- 
diately emerges  for  consideration  as  a  subject  of 
general  education.  The  richness  of  zoology  as  a 
science  and  its  many-sided  appeal  is  just  beginning  to 
dawn  on  those  who  arrange  courses  of  study.  Owing, 
however,  to  the  way  in  which  it  is  commonly  pursued 
attention  is  so  exclusively  confined  to  observations 
of  animals  and  the  means  of  identifying  them  that 
the  student  is  not  made  aware  of  its  other  aspects 
and,  as  a  consequence,  a  narrow  conception  of  its 
scope  has  prevailed. 

Although,  in  treatises  on  the  subject,  it  has  been 
well  expounded  from  the  standpoint  of  the  structure, 
the  development  and  the  life  histories  of  animals,  the 


2         THE  MAIN  CURRENTS  OF  ZOOLOGY 

plain  story  of  how  zoology  arose  and  of  how  it  became 
closely  related  to  human  affairs  has  not  been  told. 

There  has  been  too  little  attempt  to  picture 
zoology  as  a  unified  science.  Even  among  those  who 
have  studied  zoology,  knowledge  is  little  dissem- 
inated regarding  its  scope,  the  results,  both  material 
and  intellectual,  of  its  progress  and  the  kind  of  work 
that  is  being  carried  on  at  the  present  time.  Scarcely 
known  are  the  names  of  its  foremost  men,  their 
relative  rank  and  the  reasons  for  their  eminence. 

These  matters  are  not  only  important,  they  are 
essential  to  an  understanding  of  what  zoology  is  and 
what  it  stands  for. 

To  say  that  zoology  is  the  science  that  acquaints 
us  with  animals  and  the  phenomena  of  animal  life — 
which  is  a  fair  definition — gives  no  clue  to  the  part 
it  has  played  in  intellectual  development  and  in  the 
interpretation  of  the  organic  world.  Its  advances 
brought  a  new  class  of  ideas  into  man's  intellectual 
horizon,  which  resulted  in  dispelling  error,  in  spread- 
ing enlightenment  and  produced  some  changes  of 
opinion  of  epoch-making  importance. 

There  resulted  from  zoological  discovery  the 
sweeping  conclusion  that  the  human  body  belongs 
to  the  animal  series  and,  consequently,  that  observa- 


A  SUBJECT  OF  GENERAL  EDUCATION       3 

tions  regarding  animals  and  their  relation  to  nature 
apply  also  to  the  human  body  and  to  the  question  of 
man's  place  in  nature. 

This  truth  was  a  long  time  gaining  credence  since 
it  was  hi  conflict  with  ideas  that  had  prevailed  for 
centuries  and  its  final  acceptance  brought  a  revolu- 
tion of  opinion. 

The  recognition  of  this  oneness  of  nature,  especially 
as  applied  to  the  animal  world,  is  one  of  the  most 
dramatic  results  of  scientific  advancement.  It  is 
continually  illustrated  in  a  great  variety  of  rela- 
tions:— the  similarity  of  stages  of  embryonic  develop- 
ment of  all  animals,  the  gradual  building  of  body  and 
of  mind,  the  ultimate  bearing  of  these  questions  on 
human  origin  and  destiny.  It  led  to  the  analysis  of 
the  phenomena  of  life,  reduced  to  their  simplest 
expression  hi  the  lower  organisms,  hi  order  to  throw 
light  on  the  vital  activities  of  higher  animals.  It  also 
led  to  including  man  in  the  scheme  of  organic  evolu- 
tion and  opened  many  other  new  questions. 

Naturally,  a  subject  of  such  wide  scope  and  of 
such  varied  aspects  presents  particular  difficulties  of 
treatment  and  it  is  further  complicated  by  the 
traditional  method  of  the  study  of  animal  forms  to 
the  exclusion  of  other  major  topics.  The  question  of 


4         THE  MAIN  CURRENTS  OF  ZOOLOGY 

what  must  be  included  in  the  exposition  of  zoology 
and  what  may  be  omitted  becomes  a  perplexing  one. 

Accordingly,  at  the  outset,  it  is  of  primary  im- 
portance to  get  an  idea  of  what  is  embraced  within 
the  zoological  territory  and  to  determine  the  method 
of  analysis  so  as  to  give,  if  possible,  a  unified  view  of 
this  many-sided  science.  Undoubtedly,  the  be- 
wildering number  of  details  makes  it  difficult  to  deal 
with  them  clearly  and  coherently.  The  attempt  to 
unite  them  into  an  orderly  whole  runs  the  risk  of 
becoming  merely  discursive.  The  matter,  however,  is 
greatly  simplified  by  the  circumstance  that  in  the 
progress  of  zoology,  notwithstanding  the  continual 
multiplication  of  details,  there  has  been  continuity  of 
development  of  zoological  thought.  If  we  can  follow 
the  path,  the  large  number  of  details  serves  to  enrich 
the  subject  with  numerous  illustrations  without  con- 
fusing it. 

The  first  step  of  our  program  should  be  to  deter- 
mine the  main  currents  of  zoological  progress  and, 
thereafter,  to  become  acquainted  with  the  circum- 
stances under  which  they  were  started  and  their 
ultimate  outcome. 

The  direct  study  of  animal  types  will  not  suffice. 
Laboratory  exercises  and  observation  of  animals  in 


A  SUBJECT  OF  GENERAL  EDUCATION       5 

the  field  are  necessary,  but  experience  has  repeatedly 
shown  that  this  in  itself  is  not  sufficient.  Such 
studies  should  be  supplemented  by  the  story  of  the 
rise  of  zoology  and  a  systematic  account  of  its  dis- 
coveries of  first  magnitude. 

As  indicated  above,  these  aspects  of  zoology  are  so 
commonly  neglected  that  students  emerge  from  the 
study  of  the  subject,  possessing  only  a  certain  set  of 
facts  about  animals — with  detached  fragments  of 
zoological  knowledge — and  no  conception  of  zoology 
as  a  department  of  human  learning.  The  fact  is  that 
the  outlook  on  zoology  has  been  too  narrow,  and  we 
should  become  more  aware  of  the  results  of  zoological 
study  and  not  limit  our  vision  merely  to  facts  about 
animals — in  a  word,  more  cognizant  of  the  ideas  and 
theories  of  zoology. 

Considerations  of  this  nature  serve  to  indicate  that 
a  knowledge  of  the  main  currents  of  zoology  should 
be  acquired  in  connection  with  the  facts  of  observa- 
tion learned  in  the  laboratory  and  in  the  field.  To 
orient  ourselves  toward  the  subject  we  should  at 
least  know  the  great  movements,  the  foremost  men, 
in  a  broad  way  the  influence  of  their  researches,  and 
the  present  tendencies  of  the  science. 

It  is  the  purpose  of  the  following  chapters  to  supply 


6         THE  MAIN  CURRENTS  OF  ZOOLOGY 

such  an  account — untechnical  and  not  in  too  great 
detail.  There  are  excellent  text-books,  in  which  the 
animal  kingdom  is  systematically  considered,  but 
there  is  need  of  a  source  of  collateral  reading  to 
supplement  these  text-books  and  to  run  parallel  with 
laboratory  work  and  field  observations. 

Position  of  Zoology  in  Biology. — To  fix  the 
place  of  zoology  we  need  only  to  remember  that  one 
of  the  most  striking  developments  of  the  past  half- 
century  has  been  the  great  extension  of  knowledge  of 
organic  nature  and  the  new  interpretations  that  have 
resulted.  Since  zoology  is  the  central  subject  of 
this  biological  advance,  it  has  come  about  that  this 
science  embodies  our  interpretations  of  organic 
nature.  There  comes  within  its  province  considera- 
tion of  all  the  phenomena  of  animal  life  and  of  what 
has  grown  out  of  their  study: — Evolution,  genetics, 
heredity,  biogenesis,  Mendelism,  transmission  of 
disease  through  animal  agencies,  structure,  devel- 
opment, habits,  animal  intelligence  and  behavior. 
These  and  kindred  matters  find  in  zoology  their 
illustrations  and  their  systematic  treatment. 

Inasmuch  as  most  animals  possess  a  nervous  sys- 
tem, which  is  lacking  in  plants,  zoology  gives  a  fuller 
representation  of  vital  phenomena  than  its  sister 


A  SUBJECT  OF  GENERAL  EDUCATION       7 

science  botany,  and  it  has  been  more  intimately  con- 
cerned than  any  other  subject  in  expanding  our  ideas 
of  the  human  body  in  its  relation  to  nature. 

Owing  to  the  character  of  the  questions  involved 
and  to  its  broad  scope,  the  foremost  claim  of  zoology 
to  attention  is  as  a  subject  of  general  education. 
Education  to-day  without  some  knowledge  of  the 
phenomena  of  nature  is  inadequate.  Some  training 
in  the  scientific  method  of  observation,  such  as  is 
supplied  by  zoology,  is  an  indispensable  part  of  the 
mental  equipment  of  the  liberally  educated. 

The  results  of  zoological  investigation  have  prac- 
tical bearing  in  sanitary  science,  hi  the  conservation 
of  useful  animals,  for  the  agriculturist,  the  breeder 
and  the  economic  zoologist.  While  supplying  train- 
ing and  important  knowledge  of  the  animal  life 
referred  to,  the  subject  affords  opportunity  for 
diversion  hi  the  study  of  birds,  marine  forms  and 
insects. 

Besides  its  position  in  general  education  zoology  is 
basal  to  the  study  of  medicine.  Not  only  have 
zoological  discoveries  enriched  medicine,  but,  further- 
more, they  have  supplied  the  foundations  upon 
which  experimental  medicine  has  been  built.  Zoology 
is  one  of  the  important  pre-clinical  subjects,  and  all 


8         THE  MAIN  CURRENTS  OF  ZOOLOGY 

students  preparing  for  the  profession  of  medicine 
should  engage  in  the  study  of  zoology,  not  merely  as 
supplying  training  in  the  kind  of  observation  that  is 
needed  for  diagnosis,  but  as  affording  a  broader 
outlook  on  the  structure,  the  development  and  the 
physiology  of  the  human  body.  It  affords  to-day  the 
best  introduction  to  general  physiology. 

In  addition  to  its  inseparable  connections  with 
botany,  zoology  is  closely  related  to  two  other 
sciences — physics  and  chemistry.  Zoology  and 
botany  are  essentially  the  sciences  of  organic  nature, 
while  physics  is  the  science  of  inorganic  nature.  In 
the  study  of  nature  the  biological  and  physical 
sciences  are  fundamental  and  reciprocal  to  one  an- 
other. 

Chemistry  is  somewhat  more  closely  allied  to 
biological  phenomena  since  these  phenomena  are 
physico-chemical  in  their  nature  and  the  great 
development  of  physiological  chemistry  has  brought 
it  into  very  close  relation  with  biology.  A  certain 
knowledge  of  chemistry  is  necessary  to  the  under- 
standing of  any  physiological  problem.  Chemistry, 
physics  and  biology  form  the  tripod  of  sciences 
essential  to  the  student  of  medicine. 

Zoology  has  been  made  by  the  confluence  of  many 


A  SUBJECT  OF  GENERAL  EDUCATION       9 

scientific  currents  and  it  cannot  be  properly  treated 
in  isolation.  Especially  that  which  is  broadly 
biological  is  a  part  of  zoology  as  well  as  of  botany. 
In  attempting  to  find  the  main  currents  of  zoology 
let  us  begin  with  the  chief  biological  advances  of  the 
nineteenth  century. 


CHAPTER  II 

THE  OUTSTANDING  BIOLOGICAL  ADVANCES 
OF  THE  NINETEENTH  CENTURY 

THE  events  of  the  nineteenth  century  have  a 
relatively  near-by  interest.  Accordingly,  it  will  be 
first  in  order  to  inquire  what  are  the  biological  ad- 
vances of  widest  influence  of  the  past  century? 

Many  advanced  students  of  zoology  would  be 
puzzled  if  called  on  to  separate  the  truly  outstanding 
events  of  zoological  progress  from  those  of  subor- 
dinate importance.  There  were  so  many  biological 
advances  in  "The  Wonderful  Century"  that  the 
task  of  selecting  those  to  stand  in  the  front  rank  re- 
quires much  discrimination.  The  basis  for  selection 
is  not  the  brilliancy  of  individual  discoveries,  nor 
unprecedented  progress  in  special  fields,  but  the 
consequences  that  followed  unique  discoveries  and 
the  extent  to  which  they  influenced  the  whole  field  of 
biology. 

Instances  of  notable  advances  will  at  once  emerge 
for  consideration  such  as:  the  establishment  of 
embryology  on  modern  lines  by  Von  Baer  (1828),  the 
discovery  of  the  nucleus  of  plant  cells  by  Robert 


10 


OUTSTANDING  BIOLOGICAL  ADVANCES    n 

Brown  (1831),  the  work  of  Johannes  Mliller  in  animal 
physiology,  the  development  of  vegetable  morphol- 
ogy by  Hofmeister  and  of  vegetable  physiology  by 
Sachs  and  Pfeffer.  These  are  biological,  but  im- 
portant as  they  were,  they  did  not  influence  the  whole 
field  of  biological  science  as  did  those  events  now 
referred  to  as  the  outstanding  biological  advances  of 
the  century. 

To  avoid  repeated  explanation,  it  is  to  be  under- 
stood that  the  term  "biological"  is  generic  and  im- 
plies botanical  as  well  as  zoological  advances,  but  it  is 
used  here  in  the  restricted  sense  of  "biological" 
from  the  animal  side. 

Considered  from  the  standpoint  of  wide  influence, 
there  are  five  biological  advances  of  the  nineteenth 
century  to  which  all  others  are  subordinate.  These 
are:  the  discovery  of  protoplasm;  the  formulation  of 
the  cell- theory;  the  establishment  of  the  theory  of 
organic  evolution;  the  demonstration  of  the  germ- 
theory  of  disease  in  connection  with  the  rise  of 
bacteriology,  and,  fifth,  the  experimental  study  of 
heredity.  There  was  a  parallel  development  of 
these  subjects  but,  for  clearness,  separate  considera- 
tion is  necessary. 

The    Discovery    of   Protoplasm. — The    scientific 


12       THE  MAIN  CURRENTS  OF  ZOOLOGY 

discovery  of  protoplasm  came  in  1835,  though  its 
significance  was  not  recognized  until  twenty-five 
years  later.  This  living  substance,  common  to  plants 
and  animals,  had  been  casually  observed,  at  inter- 
vals, from  1755  onwards.  Under  the  microscope  its 
movement  had  been  detected  in  the  proteus  animal- 
cule, by  Roesel  von  Rosenhoff  in  1755.  Thereafter, 
in  plants,  by  Myen,  in  1827,  and  by  other  observers. 
But  all  these  observations  were  substantially  point- 
ing out  the  existence  of  movements  of  a  semi-trans- 
parent jelly-like  substance  in  animals  and  plants. 

An  important  forward  step  came  in  1835  when 
Felix  Dujardin  (1801-1860),  a  French  naturalist, 
published  discriminating  observations  on  this  living 
substance  in  simple  animals  such  as  various  protozoa 
and  worms.  Not  content  with  merely  observing  its 
movements,  he  experimented  with  it,  and  by  applying 
tests  as  to  its  solubility  and  behavior  towards  differ- 
ent reagents,  he  distinguished  between  it  and  gum, 
gelatine,  mucus  and  white  of  egg,  with  which  it  has 
superficial  resemblances.  Finally,  in  1835,  he  de- 
scribed it  as  a  "living  jelly  endowed  with  all  the 
properties  of  life."  His  predecessors  had  not  ob- 
served it  in  this  way;  consequently,  it  is  proper  to 
designate  Dujardin  as  the  scientific  discoverer  of 


OUTSTANDING  BIOLOGICAL  ADVANCES    13 

protoplasm.  He  called  it  sarcode,  from  the  Greek, 
meaning  flesh-like. 

Although  Dujardin  pointed  out  that  sarcode  was  a 
different  substance  from  any  other  known  to  science, 
and  that  it  was  endowed  with  all  the  properties  of 
life,  he  was  far  from  recognizing  the  distinctive  r61e 
it  plays  in  nature.  The  conclusion  prevailed  that 
it  was  confined  to  the  lower  animals,  and  this  long 
delayed  the  recognition  that  it  is  the  living  substance 
of  all  organisms — including,  of  course,  the  human 
body.  To  reach  this  point  took  twenty-five  years  of 
investigation  by  various  men. 

The  name  sarcode  was  not  retained  and  the  cir- 
cumstances under  which  the  original  name  was 
changed  to  protoplasm  may  be  briefly  stated.  Eleven 
years  after  Dujardin's  discovery,  the  German  botan- 
ist, Hugo  von  Mohl  (in  1846),  described  the  same 
slimy  substance  in  plants  under  the  name  proto- 
plasma.  In  the  interval,  it  had  been  de  cribed,  in 
1840,  under  the  designation  protoplasm,  in  mamma- 
lian embryos,  by  the  Bohemian  anatomist  Purkinje". 

In  1846,  after  von  MohPs  publication,  the  scientific 
world  was  in  the  position  of  knowing  "sarcode"  of 
lower  animals,  and  "protoplasm"  in  certain  animal 
embryos  as  well  as  in  plants. 


H       THE  MAIN  CURRENTS  OF  ZOOLOGY 

There  now  began  to  rise  the  suggestion  that 
sarcode  and  protoplasm  were  different  names  for 
one  and  the  same  substance  and,  in  1850,  Ferdinand 
Cohn  definitely  maintained  that  protoplasm  and 
sarcode  were  identical  substances.  Later  in  life  Cohn 
became  eminent  for  investigations  in  bacteriology 
but,  at  this  time  he  was  a  young  man  of  twenty-two 
years  and  his  contribution  was  considered  theoretical 
and  insufficiently  supported  by  observation  and  ex- 
periment. 

With  Max  Schultze  (1825-1874),  came  the  summa- 
tion of  the  accumulated  knowledge  regarding  proto- 
plasm and  the  final  step  in  bringing  it  into  full 
recognition  in  the  scientific  world.  After  a  long 
series  of  observations  and  experiments  he  announced, 
in  1861,  that  living  substance,  be  it  called  sarcode  or 
protoplasm,  is  essentially  alike  in  animals  and  plants. 
He  reached  this  conclusion  largely  upon  physiological 
resemblances,  pointing  out,  especially,  that  the  con- 
tractility exhibited  by  all  protoplasm  is  essentially 
similar  to  the  contraction  of  muscles. 

One  thing  that  had  stood  in  the  way  of  an  earlier 
recognition  of  the  true  nature  of  protoplasm  was, 
that  for  some  years,  it  was  supposed  to  be  confined 
to  lower  animals  and  it  was  necessary  that  observa- 


OUTSTANDING  BIOLOGICAL  ADVANCES    15 

tion  should  establish  that  it  is  universal  in  all  or- 
ganisms before  the  general  conclusion  could  be 
reached. 

Let  us  now  estimate  the  consequences  of  the  dis- 
covery of  protoplasm.  Here  for  analysis  we  have 
disclosed  the  living  substance  of  all  animals  and 
plants.  In  this-  physical  substratum  all  vital  ac- 
tivities exhibit  their  manifestations.  Now  for  the 
first  time  was  recognized  the  basis  of  physiological 
activities.  If  the  naturalist  is  ever  to  bring  vital 
activities  under  close  analysis,  he  must  do  so  by 
hemming  acquainted  with  the  properties  and  the 
behavior  of  protoplasm.  Even  in  its  simplest  form 
it  exhibits  the  germ  of  all  properties  that  appear 
better  developed  in  higher  organisms. 

The  recognition  of  the  nature  of  protoplasm,  to- 
gether with  the  adoption  of  the  cell-theory,  led  to  the 
foundation  of  modern  biology,  and  the  progress  of 
biology,  since  1861,  has  been  largely  a  matter  of 
becoming  better  acquainted  with  protoplasm.  By 
means  of  these  discoveries  vital  phenomena  were  seen 
in  a  new  light  and  progress  was  started. 

It  is  to  be  remembered  throughout  this  book  that  a 
great  scientific  discovery  is  never  the  product  of  one 
man,  nor  of  two  men.  Although  in  bringing  forward 


16       THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  protoplasm  idea,  Dujardin  (Fig.  i)  and  Max 
Schultze  (Fig.  2)  occupy  the  foremost  position,  a 
great  many  other  investigators,  as  the  botanists 
De  Bary,  Nageli,  Strassburger  and  others  contrib- 
uted to  this  end. 

The  Cell-Theory.— The  cell-theory  had  a  parallel 
development  with  the  protoplasm  idea  and,  ulti- 
mately, they  fused  as  one.  The  cell-theory  was  an- 
nounced in  1838-1839,  a  few  years  after  Dujardin's 
discovery  of  protoplasm. 

The  microscopic  examination  of  a  thin  section  of  a 
plant  stem,  a  similar  section  of  hardened  liver, 
scrapings  from  the  inside  of  the  human  cheek,  the 
skin  of  a  frog,  the  skin,  or  epidermis,  of  a  plant,  all 
reveal  similar  units  of  organic  architecture.  Further 
studies  show  that  brain  tissue,  bone  and  cartilage,  in 
fact,  all  organic  tissues  are  constructed  by  the  union 
of  microscopic  elements  nicely  fitted  in  together. 
This  is  the  basis  of  the  cell-theory,  but  it  is  a  long 
step  from  mere  observation  of  these  elements  to  the 
generalization  that  all  animals  and  plants  are  com- 
posed of  a  union  of  similar  cells.  The  latter  concep- 
tion in  its  full  sweep  unites  all  living  creations  on  the 
broad  plane  of  similarity  of  structure  and,  as  we  shall 
soon  see,  of  similarity  of  origin — since  all  organisms, 


FlG>  L —FELIX  DUJARDIN  (1801-1860)      FIG.  2.— MAX  SCHULTZE  (1825-1874)  * 


FIG.  3. — THEODOR  SCHWANN  (1810-1882)  FIG.  4. — THEODOR  BOVERI  (1866-1916) 


OUTSTANDING  BIOLOGICAL  ADVANCES    17 

no  matter  how  complex,  begin  their  existence  in  the 
condition  of  a  single  cell. 

This  "master-stroke  of  generalization"  had  a 
wonderful  unifying  effect  in  bringing  all  animals  and 
plants  under  one  view  as  to  origin  and  structure. 

The  names  of  two  men,  Schleiden  and  Schwann, 
are  associated  with  the  launching  of  this  theory. 
Schleiden  was  a  botanist,  and  Schwann,  an  anat- 
omist— a  happy  combination  in  biological  investi- 
gation. They  are  commonly  spoken  of  as  the 
co-founders  of  the  cell-theory.  This  statement,  how- 
ever, requires  qualification,  for  the  part  played  by 
the  two  men  was  very  unequal.  Schwann,  so  to 
speak,  was  the  star  and  Schleiden  played  a  subordi- 
nate part. 

Schleiden's  work  was  auxiliary.  He  had  observed 
cell  formation  and  cell  structure  of  plants  and  pub- 
lished a  small  paper  on  this  subject  in  1838.  In  a 
friendly  conference,  he  assisted  Schwann,  whose 
researches  were  already  the  more  extensive,  by  sug- 
gesting that  the  nucleus  (cytoblast)  of  the  animal 
tissues,  examined  by  Schwann,  was  the  same  as  the 
nucleus  of  plants  and  this,  apparently,  flashed  into 
the  mind  of  Schwann,  the  identity  of  organization  of 
animals  and  plants. 


i8       THE  MAIN  CURRENTS  OF  ZOOLOGY 

Schwann  (Fig.  3)  in  an  extensive  paper  (215  octavo 
pages,  with  four  plates),  published  in  1839  first  em- 
ployed the  term  "cell- theory"  and  explained  its 
meaning.  This  treatise,  which  is  a  biological  classic, 
was  his  famous  Microscopical  Researches  regarding 
the  Accordance  in  Structure  and  Growth  of  Animals  and 
Plants  (Mikroscopische  Untersuchungen  uber  die 
Uebereinstimmung  in  der  structur  und  dem  Wach- 
sthum  der  Thiere  und  Pflanzen). 

Schwann's  writing  in  the  Microscopical  Researches 
is  clear  and  philosophical,  and  is  divided  into  three 
sections,  in  the  first  two  of  which  he  confines  himself 
strictly  to  descriptions  of  observations,  and  in  the 
third  part  of  which  he  enters  upon  a  philosophical 
discussion  of  the  significance  of  the  observations. 
He  comes  to  the  conclusion  that:  "The  elementary 
parts  of  all  tissues  are  formed  of  cells  in  an  analogous, 
though  very  diversified  manner,  so  that  it  may  be 
asserted  that  there  is  one  universal  principle  of  devel- 
opment of  the  elementary  parts  of  organisms,  how- 
ever different,  and  that  this  principle  is  the  formation 
of  cells." 

It  was  in  this  treatise  also  that  he  introduced  the 
term  cell- theory  as  follows:  "The  development  of  the 
proposition  that  there  exists  one  principle  for  the 


OUTSTANDING  BIOLOGICAL  ADVANCES    19 

formation  of  all  organic  products,  and  that  this 
principle  is  the  formation  of  cells,  as  well  as  the  con- 
clusions which  may  be  drawn  from  this  proposition, 
may  be  comprised  under  the  term  cell-theory,  using 
it  hi  its  more  extended  signification,  while,  in  a  more 
limited  sense,  by  the  theory  of  cells  we  understand 
whatever  may  be  inf erred  from  this  proposition  with 
respect  to  the  powers  from  which  these  phenomena 
result." 

Schleiden  had  not  used  the  term  cell-theory,  nor 
developed  the  ideas  at  the  basis  of  it,  accordingly  it  is 
more  proper  to  give  the  credit  to  Schwann  for  this 
great  generalization  and  to  speak  of  it  as  the  cell- 
theory  of  Schwann  rather  than  the  cell-theory  of 
Schleiden  and  Schwann. 

There  were  serious  defects  in  the  theory  as  it 
existed  in  the  minds  of  the  early  observers.  Both 
Schleiden  and  Schwann  attached  importance  to  the 
cell-wall  and  had  a  wrong  idea  of  the  nucleus  (called 
cytoplast  by  Schleiden)  and  of  the  formation  of  cells. 
But,  as  researches  progressed,  the  theory  was  greatly 
expanded  and  unproved. 

One  of  the  most  helpful  steps  was  the  full  recogni- 
tion of  the  origin  of  cells  in  multicellular  organisms. 
The  many-celled  animals  and  plants  begin  then- 


20       THE  MAIN  CURRENTS  OF  ZOOLOGY 

existence  in  the  condition  of  a  single  cell,  and  from 
this  primary  condition,  the  many  cells  arise  by 
successive  divisions  of  the  original  one.  These  many 
cells  become  separated  into  different  groups  which 
exhibit  different  properties,  and,  by  the  combination 
of  cells  having  similar  properties,  the  tissues  arise. 
When,  finally,  about  1865,  all  eggs,  as  well  as  their 
fertilizing  agents,  or  sperms,  were  recognized  as  cells, 
we  had  the  logical  explanation  of  the  origin  of  cells, 
and,  also,  an  insight  into  the  nature  of  tissues. 

At  the  time  of  Schleiden  and  Schwann  a  cell  was 
thought  of  as  a  box-like  compartment  or  a  little  space 
surrounded  by  walls  but,  presently,  this  conception 
was  materially  changed.  The  cell- wall  was  seen  to  be 
formed  by  the  living  protoplasm  within,  and  atten- 
tion became  directed  to  that  substance  as  the  essen- 
tial part  of  the  cell.  Many  animal  cells  were  observed 
without  cell-walls  and  the  conclusion  was  soon  reached 
that  the  cell-wall  is  unimportant  and  may  be  lacking. 
Accordingly,  about  1860,  Max  Schultze  defined  the 
essential  qualities  of  a  cell  as  "A  mass  of  protoplasm 
containing  a  nucleus."  Up  to  this  time  the  cell-theory 
was  chiefly  a  morphological  doctrine,  but  now  com- 
bined with  the  protoplasm  idea,  which  was  essentially 
physiological,  it  assumed  a  wider  significance. 


OUTSTANDING  BIOLOGICAL  ADVANCES    21 

From  this  point  ideas  began  to  broaden  and  other 
new  relations  were  discovered.  The  minute  struc- 
ture of  the  cell  was  investigated,  the  centrosome  and 
the  chromosomes  were  discovered,  the  behavior  of 
these  parts  and  of  the  nucleus  were  observed.  The 
phenomena  of  fertilization  of  the  egg,  the  mechanism 
of  heredity  and  the  seat  of  hereditary  qualities  were 
studied  as  problems  pertaining  to  cell  life. 

So  many  sweeping  conclusions  resulted  that  a 
new  branch  of  biology  having  to  do  with  the  phenom- 
ena of  cellular  life  was  organized.  This  division  was 
called  cytology  and  the  late  Theodor  Boveri  (1866- 
1916)  (Fig.  4),  was  perhaps  its  leading  representative 
on  the  zoological  side. 

In  its  modern  statement  the  cell-theory  has  come 
to  embrace  four  aspects  which  successively  have  been 
developed.  These  are :  the  conceptions  of  the  cell  as  a 
unit  of  structure;  the  cell  as  a  unit  of  physiology;  the 
cell  in  development  and  in  heredity.  The  title  of 
Wilson's,  now  classic,  book  on  The  Cell  in  Develop- 
ment and  Inheritance  carries  this  idea.  (For  com- 
ments on  the  cell  in  inheritance  see  p.  43.) 

From  these  considerations  it  becomes  evident 
that  the  cell-theory  and  the  protoplasm  idea  are 
broad  generalizations  that  influenced  the  entire 


22       THE  MAIN  CURRENTS  OF  ZOOLOGY 

field  of  biology  and  classes  them  as  outstanding 
advances. 

The  Doctrine  of  Organic  Evolution. — The  doc- 
trine of  organic  evolution  is  so  comprehensive  in  its 
range  that  it  has  entered  into  the  whole  frame-work 
of  human  thinking  and  its  acceptance  has  so  pro- 
foundly changed  conceptions  of  man  and  nature  that 
it  has  produced  a  great  mental  revolution.  There  is  a 
natural  cleavage  between  thought  before  1859  and 
thought  after  that  date  regarding  the  biological 
interpretation  of  the  universe.  The  doctrine  of 
organic  evolution  has  done  more  to  enrich  zoology 
than  any  other  advance.  In  its  full  sweep  it  is  one  of 
the  greatest  acquisitions  of  human  knowledge.  Al- 
though utilized  in  different  departments  of  learning 
it  is  a  biological  doctrine  and  receives  its  fullest 
illustration  in  zoology.  It  is  the  recognition  that  the 
higher  animals  have  been  derived  by  modification 
from  the  simpler  ones  and  it  cleared  up  many  of  their 
heretofore  perplexing  relations.  It  is  the  discovery  of 
the  lineage  of  animals  and  plants. 

Although  it  is  commonly  believed  that  Charles 
Darwin  (Fig.  5)  was  the  founder  of  this  doctrine  it 
was  clearly  expressed  more  than  fifty  years  before 
the  publication,  in  1859,  of  Darwin's  Origin  of 


FIG.  5. — CHARLES  DARWIN  (1809-1882) 
A  few  years  prior  to  the  publication  of  The  Origin  of  Species 


OUTSTANDING  BIOLOGICAL  ADVANCES    23 

Species.  The  French  zoologist,  Lamarck  (1744- 
1829)  was  the  first  to  announce,  in  1801,  a  compre- 
hensive theory  of  evolution  that  has  lasted  to  the 
present,  while  Darwin's  especial  contribution  was 
the  designation  of  natural  selection  as  the  chief 
agency  in  bringing  about  the  evolution  of  animals  and 
plants.  Besides  these  two,  the  theories  of  Weismann 
and  De  Vries  have  attracted  the  most  attention. 

This  doctrine  is  so  important  and  so  intricate  that 
in  a  later  chapter  it  will  be  returned  to  for  fuller  ex- 
position of  the  different  theories. 


CHAPTER  III 

THE  OUTSTANDING  BIOLOGICAL  ADVANCES- 
CONTINUED 

AFTER  such  high  praise  of  the  theory  of  organic 
evolution,  what  can  remain  to  be  said  of  the  advance 
resulting  from  the  biological  work  of  Pasteur,  Koch 
and  Lister? 

The  theory  of  Organic  Evolution  is  philosophical 
and  wide-reaching,  but  the  results  of  the  study  of 
micro-organisms,  with  which  Pasteur  and  others  were 
concerned,  had  more  immediate  practical  applica- 
tions. 

The  science  of  bacteriology  embraces  several 
general  questions  such  as,  the  germ-theory  of  disease, 
the  nature  of  fermentation,  of  inflammations,  the 
spontaneous  origin  of  life,  immunity,  etc.  In  this 
group  of  topics  certain  animal  and  plant  organisms 
are  so  intertwined  as  to  their  aspects  and  effects  that 
it  is  artificial  to  attempt  to  draw  a  sharp  line  sep- 
arating the  bacteria  from  all  other  organisms.  When 
strictly  limited,  bacteriology  should  be  confined  to 
bacteria,  which  are  minute  plants,  but,  as  the  experi- 
mental study  of  these  micro-organisms  advanced,  it 

24 


OUTSTANDING  BIOLOGICAL  ADVANCES    25 

was  inevitable  that  some  minute  animal  organisms 
also  should  become  involved.  This  overlapping  of 
closely  related  fields  of  investigation  is  so  common 
that  it  may  be  accepted  as  characteristic. 

For  our  present  purpose  we  shall  not  take  up 
specifically  the  various  topics,  mentioned  above, 
but,  under  the  general  caption  Bacteriology,  treat 
in  a  general  way  of  the  movement  and  its  re- 
sults. 

Rise  of  Bacteriology. — The  rise  of  bacteriology 
with  its  germ-theory  of  disease  had  far-reaching 
consequences  for  the  benefit  of  mankind;  there  is, 
in  fact,  no  biological  advance  that  has  had  more 
important  bearings  on  the  welfare  of  the  human 
race. 

The  micro-organisms  are  so  minute  that  one  would 
scarcely  expect  them  to  play  an  important  part  in 
human  affairs.  The  world  of  exceedingly  minute 
life  was  first  exposed  by  the  Dutch  microscopist, 
Leeuwenhoek,  who,  in  1675,  discovered  the  protozoa 
and,  in  1683,  the  bacteria.  The  protozoa  are  micro- 
scopic animals  while  the  bacteria  are  microscopic 
plants.  The  more  general  term  micro-organisms  is 
convenient  as  it  includes  them  both — and,  of  course, 
other  minute  plants  that  are  not  bacteria.  It  was 


26       THE  MAIN  CURRENTS  OF  ZOOLOGY 

nearly  two  centuries  after  Leeuwenhoek's  discovery 
before  these  organisms  began  seriously  to  be  con- 
sidered as  of  practical  interest. 

We  cannot  assign  a  definite  date  as  the  time  of  the 
beginning  of  bacteriology.  It  took  form  gradually. 
The  researches  of  Ferdinand  Cohn  on  the  bacteria, 
published  at  various  times  between  1853  and  1872, 
form  an  important  preliminary  preparation.  This  is 
especially  true  of  his  classification  of  the  bacteria 
which  in  its  larger  features  is  essentially  the  one  used 
to-day.  If,  however,  any  single  man  is  to  be  con- 
sidered as  the  founder  of  bacteriology  that  man  is 
Louis  Pasteur,  while  for  Robert  Koch  we  reserve  the 
distinction  of  having  lifted  it  into  the  position  of  an 
independent  science. 

For  convenience  we  may  arbitrarily  adopt  the 
date  1877,  as  being  the  time  when  bacteriology 
sprang  into  general  recognition.  In  that  year  both 
Pasteur  and  Koch  demonstrated  that  splenic  fever,  a 
specific  disease  of  sheep  and  cattle,  is  owing  to  the 
growth  within  the  body  of  a  specific  micro-organism 
called  the  anthrax  bacillus  (Bacillus  anthracis). 
Previously,  Pasteur  had  shown  the  nature  of  fer- 
mentations (1857)  and  discovered  the  connection 
between  microscopic  particles  and  silk-worm  diseases 


OUTSTANDING  BIOLOGICAL  ADVANCES    27 

(1865),  while  Robert  Koch  in  1876  had  made  a 
study  of  the  growth  of  the  anthrax  bacillus. 

In  the  early  days,  the  men  chiefly  concerned  in 
bringing  bacteriology  into  practical  use  were  Pasteur, 
Koch  and  Lister— all  great  benefactors  to  the  race. 

Pasteur. — The  brilliant  work  of  Pasteur  (1822- 
1895),  Fig.  6,  belongs  to  all  biology.  Starting  his 
scientific  career  as  a  chemist,  he  was  soon  drawn  into 
the  investigation  of  biological  problems,  and,  through 
his  later  work,  came  to  be  recognized  as  one  of  the 
foremost  men  of  biological  history.  He  left  a  heritage 
of  priceless  value  which  will  make  his  fame  as  en- 
during as  that  of  Aristotle.  His  supreme  service  was 
in  applying  the  results  of  biological  investigation  to 
the  benefit  of  mankind. 

In  laying  the  foundations  of  micro-parasitology 
(about  1877),  Pasteur  opened  a  subject  that  over- 
laps the  different  conventional  division  of  biology, 
and  his  foundations  have  been  built  upon  by  bota- 
nists, zoologists  and  physicians.  His  investigations 
gave  an  immense  impulse  to  the  study  of  pathogenic 
organisms;  and  while  his  researches  supplied  the 
foundations  of  scientific  medicine,  at  the  same  time 
they  opened  investigations  in  the  life-history  of 
micro-organisms  that  have  been  extensively  devel- 


28       THE  MAIN  CURRENTS  OF  ZOOLOGY 

oped  by  zoologists — as  in  the  notable  work  of  Fritz 
Schaudinn  and  others. 

One  of  Pasteur's  early  triumphs  was  the  demon- 
stration of  the  nature  of  fermentation  (1857).  This 
process,  which  is  so  important  in  physiology,  was 
declared  to  be  due  merely  to  chemical  action,  but 
Pasteur  showed  that  it  depends  on  the  growth  of 
living  micro-organisms,  and  he  won  his  case  against 
the  great  opposition  of  the  chemist  Liebig. 

Against  his  inclinations  Pasteur  was  forced  into 
the  controversy  (with  Pouchet),  concerning  the 
spontaneous  generation  of  life,  and,  in  1862,  made  his 
decisive  and  epoch-making  demonstrations — that  life 
is  formed  in  nutrient  fluids  only  when  living  germs  are 
allowed  to  enter  from  the  outside.  All  this  directed 
attention  to  the  constitution  of  the  floating  matter  of 
the  air.  The  impalpable  dust  that  is  always  present 
and  that  shows  in  the  path  of  a  sunbeam  through  a 
darkened  room  is  of  complex  composition — besides 
particles  of  non-living  matter  there  are  living  or- 
ganisms of  different  kinds  in  a  dried  condition. 
Some  of  these  are  harmless  and  others  are  disease 
producing.  When  floating  germs  are  introduced  into 
canned  fruits  and  meats,  they  grow  and  cause  them 
to  spoil.  Other  kinds  entering  wounds  produce 


FIG.  6. — Louis  PASTEUR  (1822-1895) 


OUTSTANDING  BIOLOGICAL  ADVANCES    29 

suppuration  and  other  diseased  conditions.  Still 
other  kinds  may  produce  diseases  when  breathed  into 
the  lungs,  or,  introduced  into  the  body  through  milk, 
water  and  various  kinds  of  food.  These  discoveries 
are  of  the  utmost  importance. 

Those  micro-organisms  that  cause  canned  fruits 
and  tinned  meats  to  decompose  are  killed  by  heating 
and  when,  thereafter,  the  cans  are  securely  sealed  the 
contents  are  preserved  in  a  wholesome  condition. 
Even  more  important  than  this  was  the  recognition 
(1865-1867)  of  the  Edinburgh  surgeon,  Lister 
(Fig.  7)  that  to  keep  the  floating  germs  from  surgical 
wounds  would  prevent  gangrene  and  pus  formation. 
Against  great  ridicule  and  opposition,  Lister  made  his 
experiments,  using  carbolic  acid  dressings  and  great 
cleanliness  and,  about  1867,  established  the  method 
of  antiseptic  surgery.  This  followed  as  a  conse- 
quence of  Pasteur's  studies  but  the  credit  for  this 
application  belongs  to  Lister  (1827-1912).  At  first 
it  made  slow  progress  against  the  contemptuous 
criticisms  of  medical  men,  but  the  successes  that 
accompanied  its  practice  were  so  overwhelming 
that  this  great  advance  in  surgery  became  estab- 
lished. 

Pasteur  was  soon  led  to  experiment  with  diseases  of 


30       THE  MAIN  CURRENTS  OF  ZOOLOGY 

animals  such  as  splenic  fever  of  sheep,  cholera  of 
swine  and  fowls,  and,  through  his  efforts,  and  those 
of  contemporary  workers,  it  was  repeatedly  demon- 
strated that  a  particular  micro-organism  is  the  cause 
of  a  particular  disease.  That  most  disease  organisms 
produce  poisons  or  toxins  within  the  system  was 
demonstrated  and,  thereupon,  Pasteur  began  success- 
ful attempts  to  produce  serums,  vaccines  and  anti- 
toxins to  counteract  the  poisons  produced  by  the 
growth  of  disease  germs  within  the  body. 

Progressing  by  a  series  of  ascending  steps  he 
finally  (about  1880)  turned  his  attention  from 
animal  diseases  to  infectious  diseases  of  the  human 
body,  and  there  he  applied  the  same  principle  in  the 
production  of  antitoxin  injections. 

Having  proved  the  efficacy  of  vaccines  in  animal 
diseases  Pasteur  devoted  himself  to  the  means  of 
combating  diseases  of  the  human  body.  He  chose  a 
comparatively  obscure  human  disease,  hydrophobia, 
but  as  results  showed  made  a  wise  selection,  and  in 
working  it  out  to  a  successful  conclusion  he  estab- 
lished the  principles  on  which  future  advances  were 
to  be  made.  In  1880  he  was  already  engaged  in  the 
study  of  hydrophobia  and  in  1885  he  made  his  first 
treatment  of  a  human  being — a  young  boy  from 


OUTSTANDING  BIOLOGICAL  ADVANCES    31 

Alsace.  This  treatment  was  successful  as  his  in- 
oculation of  animals  had  been. 

The  time  had  now  come  for  the  establishment  of 
the  Pasteur  Institute  which  was  opened  in  Paris  in 
1888.  This,  the  first  institute  of  its  kind,  became 
the  parent  of  numerous  similar  institutions  that  have 
been  established  in  many  cities  throughout  the 
civilized  world. 

As  Frankland  says  in  his  Life  of  Pasteur: — "The 
extraordinary  enthusiasm  which  accompanied  the 
foundation  of  this  great  Institution  has  certainly 
not  been  equaled  in  our  time."  This  took  popular 
form.  "  Considerable  sums  of  money  were  subscribed 
in  foreign  countries  whilst  contributions  poured  in 
from  every  part  of  France.  Even  the  inhabitants  of 
obscure  little  towns  and  villages  organized  fetes  and 
clubbed  together  to  send  then-  small  gifts."  With  the 
lively  appreciation  of  the  French  for  science  and  its 
unselfish  achievements  the  opening  of  the  Institute 
was  regarded  as  of  national  importance.  On  Novem- 
ber 14,  1888,  it  was  opened  with  impressive  cere- 
monies presided  over  by  the  President  of  the  French 
Republic.  Thus,  after  a  long  period  of  struggle  and 
strong  opposition  such  as  often  falls  to  the  lot  of 
innovators,  Pasteur  came  to  honor  and  recognition. 


32       THE  MAIN  CURRENTS  OF  ZOOLOGY 

The  Pasteur  Institute  must  not  be  thought  of  as 
founded  chiefly  for  the  treatment  of  hydrophobia — 
this  is  merely  incidental.  It  is  organized  for  the 
complete  investigation  of  bacteria  and  all  manner  of 
serum  injections  and  vaccines  for  the  control  of 
diseases.  In  the  Paris  Institute,  Emile  Roux,  the 
present  Director,  perfected  and  proved  the  efficacy 
of  the  antitoxin  of  diphtheria  (independently  dis- 
covered by  Behring  in  1892) .  From  it  has  emanated, 
directly  or  indirectly,  such  important  procedure  as 
vaccination  against  typhoid  fever,  the  serum  treat- 
ment of  bubonic  plague,  etc.  Without  the  superb 
work  of  Pasteur  these  advances  could  not  have  taken 
place. 

Koch. — Robert  Koch  (Fig.  8)  was  born  in  1843, 
and  for  several  years  before  his  death  in  1910,  he  was 
the  Director  of  the  Institute  for  Infectious  Diseases 
in  Berlin.  His  investigations  were  mainly  those  of  a 
medical  man  and  were  crowned  with  remarkable 
success.  In  1881,  he  discovered  the  bacillus  of 
tuberculosis,  in  1883,  the  specific  germ  of  Asiatic 
cholera,  and  since  that  time  his  name  has  been  con- 
nected with  many  notable  discoveries  that  are  of 
continuous  practical  application  in  the  science  of 
medicine.  He  was  so  ingenious,  so  highly  trained  and 


OUTSTANDING  BIOLOGICAL  ADVANCES    33 

so  incisive  in  analysis,  that  from  time  to  time  he  was 
called  on  by  different  countries  to  assist  in  the  in- 
vestigation of  the  causes  and  means  of  control  of 
infectious  diseases — such  as  Asiatic  cholera,  the 
bubonic  plague  and  the  sleeping  sickness  of  Africa. 
Koch  was  intimately  concerned  in  establishing 
bacteriology  as  an  independent  science.  In  1882,  he 
introduced  into  bacteriological  study  the  ingenious 
method  of  employing  solid  culture  media.  Bacteria 
are  so  minute  that  it  was  a  perplexing  problem  to 
separate  the  several  forms  that  are  commonly  mixed 
and  to  secure  a  pure  culture  of  one  kind.  This  was 
made  possible  by  placing  a  liquid  culture  of  the  mixed 
bacteria  in  melted  gelatine — and  other  media  ren- 
dered liquid  by  heat.  This  mixture  was  stirred  with  a 
glass  rod  and  by  this  means  the  bacteria  were  sep- 
arated and  distributed.  The  melted  gelatine  was 
now  allowed  to  flow  over  a  sterilized  glass  plate, 
making  a  thin  film  which  hardened  on  cooling.  In 
this  manner  the  separated  bacteria  were  held  in  place 
and  as  they  grew  in  clusters,  there  were  spots  of  pure 
or  nearly  pure  culture.  These  spots  were  observed 
under  the  microscope,  were  picked  off  and  planted 
again  in  liquid  gelatine  and  the  process  repeated 
until  pure  cultures  were  secured. 


34       THE  MAIN  CURRENTS  OF  ZOOLOGY 

These  methods  so  obscure,  and,  at  first,  so  difficult 
to  ferret  out  are  now  commonly  demonstrated  in 
schools  and  training  institutions.  Many  simple 
experiments  are  now  tried  which  give  evidence  of 
the  presence  of  these  very  minute  germs  in  the  air. 
By  exposing  plates  of  sterilized  gelatine  in  shallow 
dishes  with  glass  covers  to  keep  out  germs,  in  a  room 
before  and  after  sweeping,  in  crowded  school  rooms 
and  in  open  country  air,  by  allowing  tap  water  to 
trickle  across  a  sterilized  gelatine  film,  by  allowing  a 
fly  to  walk  upon  it,  etc.  By  these  means  the  sterilized 
plates  become  infected,  they  are  immediately  covered 
and  set  away  in  a  warm  place.  The  growth  of  bac- 
teria on  the  gelatine  produces  easily  seen  patches 
and  give  evidence  of  the  existence  of  these  germs 
which,  individually,  can  be  detected  only  by  high 
magnification.  It  is  obvious  that  the  rise  of  bac- 
teriology with  its  special  problems  exerted  wide 
influence  on  all  biological  science  and  this  justifies 
classifying  it  with  the  outstanding  advances  of  the 
century. 

The  Experimental  Study  of  Heredity.— The  in- 
vestigation of  heredity  is  of  surpassing  interest. 
There  are  so  many  theoretical  and  practical  questions 
involved.  Perennial  is  the  wish  to  know  the  way  in 


OUTSTANDING  BIOLOGICAL  ADVANCES    35 

which  hereditary  qualities  are  passed  from  genera- 
tion to  generation  and  the  conditions  under  which 
they  are  transmitted  and  by  which  they  are  qualified. 
This  has  led  to  much  speculation  and  the  formulation 
of  various  temporary  theories  of  heredity  that  have 
given  way  to  better  ones.  It  is  a  long  and  involved 
story  to  trace  the  transformations  of  these  theories, 
but,  it  may  be  said  in  a  word,  that,  in  the  last  decade 
of  the  nineteenth  century,  they  were  replaced  by  the 
theory  of  germinal  continuity — one  of  the  most 
fruitful  ideas  of  nineteenth  century  zoology.  This 
idea  will  be  returned  to  under  the  evolution  theory  of 
Weismann. 

The  theories  referred  to  were  chiefly  the  result  of 
speculative  thinking,  and  more  promising  avenue?* 
were  opened  through  the  application  of  experiment. 

The  application  of  experimental  and  of  statistical 
methods  to  the  study  of  heredity  was  brought  about 
chiefly  by  two  men — Francis  Galton,  the  English* 
man,  and  Gregor  Mendel,  an  Austrian  monk. 

Although  Mendel  conducted  his  experimental  ob- 
servations of  heredity  and  published  his  results 
(1866-1867)  before  Galton  had  fairly  begun,  we 
shall  see  that  Galton's  results  got  into  notice  before 
those  of  Mendel  and  began  to  influence  progress. 


36       THE  MAIN  CURRENTS  OF  ZOOLOGY 

Accordingly,  since  his  influence  preceded  Mendel's, 
Galton  is  commonly  recognized  as  the  founder  of 
the  scientific  study  of  heredity.  Observations  of 
"Mendelian  inheritance"  began  to  be  active  only 
after  the  opening  of-  the  twentieth  century. 

Galton. — Francis  Galton  (1822-1911)  Fig.  9,  by 
directing  attention  to  the  inheritance  of  individual 
characters  made  the  subject  of  heredity  manageable. 
Previously,  hereditary  traits  had  been  considered  in 
their  entirety,  and  the  resemblances  and  differences 
of  parents  and  their  offspring  had  been  averaged. 
This  method  was  too  diffuse,  since  no  one  could 
distinguish  sharply  among  the  multiplicity  of  char- 
acters; greater  definiteness  was  introduced  when 
Galton  began  to  study  hereditary  characters  sep- 
arately. 

Galton  was  the  grandson  of  Doctor  Erasmus 
Darwin  and  the  half  cousin  of  Charles.  After  pub- 
lishing books  on  his  travels  in  Africa,  he  began  the 
experimental  study  of  heredity,  and  in  1871,  he  read 
before  the  Royal  Society  of  London  a  paper  on  the 
theory  of  inheritance.  The  observations  upon  which 
he  based  his  conclusions  were  made  by  the  transfu- 
sion of  blood  in  rabbits  and  their  after-breeding. 
Later  he  observed  the  method  of  inheritance  of  spots 


FIG.  7. — SIR  JOSEPH  LISTER  (1827-1912)       FIG.  8. — ROBERT  KOCH  (1843-1910) 


FIG.  9. — SIR  FRANCIS  G ALTON 
(1822-1911) 


FIG.  10. — GREGOR  MEXDFL 
(1822-1884) 


OUTSTANDING  BIOLOGICAL  ADVANCES    37 

on  the  coat  of  certain  hounds,  investigated  by  statis- 
tical methods  the  inheritance  of  stature  and  of  genius 
in  human  families,  etc.  He  was  led  by  his  observa- 
tions to  formulate  a  law  of  ancestral  inheritance 
which  received  its  clearest  expression  in  his  book, 
Natural  Inheritance,  published  in  1889. 

He  was  so  deeply  interested  in  Eugenics — the 
investigation  of  the  conditions  that  improve,  or 
impair,  the  races  of  animals — that  he  is  to  be  re- 
membered as  the  founder  of  that  branch  of  biological 
knowledge. 

Mendel. — The  earliest  experimental  investiga- 
tions of  heredity  were  conducted  with  plants,  and 
the  first  epoch-making  results  were  those  of  Gregor 
Mendel  (1822-1884)  (Fig.  10),  a  monk  and  later 
abbot,  of  an  Augustinian  monastery  at  Briinn, 
Austria.  In  the  garden  of  the  monastery,  for  eight 
years  before  publishing  his  results,  he  made  experi- 
ments on  the  inheritance  of  individual  (or  unit) 
characters  in  twenty-two  varieties  of  garden  peas. 
Selecting  certain  constant  and  obvious  characters,  as 
color  and  form  of  seed,  length  of  stem,  etc.,  he  pro- 
ceeded to  cross  these  pure  races,  thus  producing 
hybrids,  and,  thereafter,  to  observe  the  results  of 
self-fertilization  among  the  hybrids. 


38       THE  MAIN  CURRENTS  OF  ZOOLOGY 

The  hybrids  were  produced  by  removing  the  un- 
ripe stamens  of  certain  flowers  and  later  fertilizing 
them  by  ripe  pollen  from  another  pure  breed  having 
a  contrasting  character.  The  results  showed  that 
only  one  of  a  pair  of  unit  characters  appeared  in  the 
hybrids  of  the  next  generation,  while  the  other  con- 
trasting character  lay  dormant.  Thus,  in  crossing  a 
yellow-seeded  with  a  green-seeded  pea,  the  hybrid 
generation  showed  only  yellow  seeds.  The  char- 
acter thus  impressing  itself  on  the  entire  progeny  was 
called  dominant,  while  the  other  that  was  held  in 
abeyance  was  designated  recessive. 

That  the  recessive  color  was  not  blotted  out  was 
clearly  demonstrated  by  allowing  the  hybrid  genera- 
tion to  develop  by  self-fertilization.  Under  these 
circumstances  a  most  interesting  result  was  attained. 
The  filial  generation,  derived  by  self-fertilization 
among  the  hybrids,  produced  plants  writh  yellow  and 
green  seeds,  but  in  the  ratio  of  three  yellow  to  one 
green.  All  the  green-seeded  individuals  and  one- 
third  of  the  yellow  proved  to  breed  true,  while  the 
remaining  two-thirds  of  the  yellow-seeded  plants, 
when  self -fertilized,  produced  yellow  and  green  seeds 
in  the  ratio  of  three  to  one. 

Subsequent  breedings  gave  an  unending  series  of 


OUTSTANDING  BIOLOGICAL  ADVANCES    39 

results  similar  to  those  obtained  with  the  first  filial 
generation. 

This  great  principle  of  alternative  inheritance  was 
exhibited  throughout  the  extensive  experiments  of 
Mendel,  and  it  is  now  recognized  as  one  of  the  great 
biological  discoveries  of  the  nineteenth  century. 
Mr.  R.  C.  Punnett  gives  (1905)  a  remarkably  clear 
and  terse  statement  of  the  facts  as  follows:  "When- 
ever there  occurs  a  pair  of  differentiating  characters, 
of  which  one  is  dominant  to  the  other,  three  possibil- 
ities exist:  there  are  recessives  which  always  breed 
true  to  the  recessive  character;  there  are  dominants 
which  breed  true  to  the  dominant  character,  and  are 
therefore  pure;  and,  thirdly,  there  are  dominants 
which  may  be  called  impure,  and  which  on  self- 
fertilization  (or  in-breeding  where  the  sexes  are 
separate)  give  both  dominant  and  recessive  forms  in 
the  fixed  proportion  of  three  of  the  former  to  one  of 
the  latter." 

The  results  of  MendePs  experiments  are  the  con- 
sequence of  the  fact  that  the  germ-cells  retain  their 
purity  with  respect  to  unit  characters.  That  is,  in 
the  combination  of  germ-cells  by  cross-breeding,  the 
hereditary  qualities  do  not  lose  their  individuality — 
they  are  mixed  but  not  blended.  When  the  germinal 


40       THE  MAIN  CURRENTS  OF  ZOOLOGY 

elements  are  formed  in  these  hybrid  plants  two 
classes  of  germ-cells  will  arise  in  equal  number,  one 
class  carrying  the  dominant  and  the  other  the  reces- 
sive quality.  Chance  combinations  of  these  germ- 
cells  will  yield  on  the  average,  one  union  of  dominant 
with  dominant,  one  union  of  recessive  with  recessive, 
and  two  combinations  in  which  dominant  and  reces- 
sive are  united.  In  the  latter  instance  the  dominant 
will  be  the  visible  character,  the  recessive,  though 
present,  being  invisible.  This  segregation  of  the 
gametes  into  two  sets  of  "pure"  gametes  was  recog- 
nized by  Mendel  in  an  attempted  theoretical  explana- 
tion of  his  observed  facts,  and,  in  view  of  the  state  of 
knowledge  at  the  time,  showed  remarkable  analytical 
ability. 

MendePs  papers  were  published  in  1866  and  1867  in 
the  proceedings  of  the  Natural  History  Society  of 
Briinn,  but  their  importance  was  overlooked  for 
nearly  thirty-five  years.  The  periodical  in  which 
they  appeared  was  not  widely  known,  and  moreover, 
the  minds  of  naturalists  at  that  time  were  largely 
occupied  with  the  questions  of  organic  evolution 
raised  through  the  publications  of  Darwin.  In  the 
year  1900,  however,  the  great  principle  of  heredity 
worked  out  by  Mendel  was  independently  redis- 


OUTSTANDING  BIOLOGICAL  ADVANCES    41 

covered  by  the  botanists  De  Vries,  Torrens,  and 
Tschermak.  By  searching  the  literature  for  anticipa- 
tions of  their  results,  the  unrecognized  papers  of 
Mendel  were  brought  to  light  and  made  generally 
known  to  the  scientific  world. 

Since  1900,  extensive  experiments  by  Bateson  and 
many  others  have  served  to  confirm  and  extend 
Mendel's  discovery.  In  the  United  States  the  experi- 
ments of  Davenport  and  of  Castle  on  inheritance  in 
poultry,  the  inheritance  of  fur  in  guinea-pigs,  erect- 
ness  of  ears  of  rabbits,  etc.,  the  far-reaching  experi- 
ments of  Morgan  with  the  fruit-fly,  as  well  as  the 
experimental  work  of  others,  have  extended  our 
knowledge  of  Mendelian  inheritance.  The  combined 
work  on  inheritance  in  animals  and  plants  of  all 
observers  has  so  thoroughly  supported  Mendel's 
conclusions,  that  the  principle  of  alternative  in- 
heritance is  commonly  spoken  of  as  Mendel's  law.1 

Other  investigations  have  led  to  the  recognition  of 
the  physical  basis  of  heredity  and  to  the  idea  of 
germinal  continuity.  Within  the  nucleus  of  cells  of 
plants  and  animals  there  are  certain  very  minute 
bodies,  the  chromosomes  (discovered  1883),  which 

1  The  seven  paragraphs  above  are  quoted  from  the  writer's  Biology  and 
Its  Makers. 


42       THE  MAIN  CURRENTS  OF  ZOOLOGY 

stain  deeply  with  micro-chemical  dyes.  These  are 
believed  to  be  the  bearers  of  heredity. 

Since  the  germinal  cells  of  plants  and  animals 
must  be  fertilized  before  they  develop,  we  find  in  the 
chromosomes  the  source  of  maternal  and  of  paternal 
qualities — because  fertilization  is  essentially  a  union 
of  the  chromosomes  of  egg  and  sperm.  Eggs  in 
getting  mature  lose  one-half  their  chromosomes, 
sperms,  or  their  fertilizing  agents,  also  in  course  of 
formation  have  their  chromosomes  reduced  by  one- 
half.  Now  the  egg  is  fertilized  by  the  union  of  the 
sperm  with  it,  and  the  fertilized  egg  is  bi-parental. 
One-half  the  chromosomes  of  the  fertilized  egg  come 
from  the  mother  and  one-half  from  the  father.  The 
maternal  chromosomes  (of  the  egg)  and  the  paternal 
(of  the  sperm)  are  the  bearers  of  the  hereditary 
qualities  of  both  parents.  In  considering  the  cell- 
theory  it  was  pointed  out  that  the  problems  of  he- 
redity are  at  bottom  cellular  problems  and  the  state- 
ments just  made  will  help  to  illustrate  that  point. 

In  closing  this  review  we  may  re-affirm,  that,  on 
account  of  their  wide  influence  on  the  entire  field  of 
biology,  the  five  events  designated  all  qualify  as 
outstanding  biological  advances  of  the  nineteenth 
century. 


CHAPTER  IV 
ZOOLOGY  EMERGES 

AFTER  analyzing  its  five  outstanding  advances  and 
before  proceeding  to  discuss  other  steps  of  biological 
progress  we  should  make  a  digression  to  consider  the 
circumstances  under  which  science  developed,  and,  in 
particular,  those  conditions  that  led  to  the  emergence 
of  zoology  as  a  separate  science. 

As  in  human  affairs  present  conditions  can  be 
understood  only  in  the  light  of  precedent  conditions, 
so  hi  zoology,  a  brief  sketch  of  its  rise  is  essential  to  an 
intelligent  comprehension  of  the  subject. 

It  is  not  necessary  to  attempt  to  picture  the  crude 
beginnings  of  observations  of  animated  nature,  and 
the  dawning  of  simple  ideas  regarding  animals  and 
plants.  The  hunters,  the  poets,  the  artists  of  an- 
tiquity and  the  primitive  nature-searchers  accumu- 
lated facts  of  observation  and  invented  many  fables 
about  animals.  Fact  and  fable  were  intermingled  and 
molded  into  a  crude  natural  history  of  animals  which 
existed  long  before  the  advent  of  Aristotle. 

Knowledge  of  nature  among  the  ancients  reached 
its  highest  development  in  the  Greek  philosopher 

43 


44       THE  MAIN  CURRENTS  OF  ZOOLOGY 

and  naturalist  Aristotle  (384-322  B.  C.)  (Fig.  n). 
He  was  a  man  of  vast  intellect  engaged  in  a  variety  of 
intellectual  occupations.  In  addition  to  writings  on 
metaphysics,  rhetoric,  etc.,  he  wrote  and  lectured  on 
the  natural  history  of  animals  (Historia  Animalium) 
as  an  independent  subject.  It  is  noteworthy  that  at 
this  early  day,  hi  his  scheme  of  zoology,  he  subor- 
dinated the  ideas  of  classification  to  his  observations 
on  structure  (De  Partibus  Animalium)  and  develop- 
ment (De  Generations  Animalium).  These  are  the 
three  books  of  Aristotle  on  zoology  that  have  been 
handed  down  to  us.  He  made  extensive  studies  of 
life  histories  and  recorded  many  facts  that  were  re- 
discovered only  in  the  nineteenth  century. 

The  circumstance  that  made  Aristotle  eminent  in 
science  (outside  his  superb  natural  talents  and  his 
industry)  was  his  method.  He  was  the  greatest  in- 
vestigator of  antiquity!  While  we  commonly  think 
of  him  as  standing  at  the  beginning  of  science,  he 
was,  in  fact,  preceded  by  a  large  number  of  observers 
whose  writings  and  verbal  utterances  are  lost.  Al- 
though living  in  the  fourth  century  before  Christ  he 
speaks  of  "the  ancients"  in  his  writings  and  says 
that  he  took  into  account  their  observations  in  estab- 
lishing his  natural  history,  but  he  says,  further,  that 


ZOOLOGY  EMERGES  45 

his  effort  to  organize  the  subject  is  the  first  attempt 
and  in  that  regard  he  had  no  forerunners. 

The  designation  "the  greatest  investigator  of 
antiquity"  is  significant  since  it  implies  that  the 
notable  development  of  science  among  the  Greeks  was 
owing  chiefly  to  their  method  of  inquiry — the  direct 
observation  of  nature  and  the  application  of  reason  to 
the  data  thus  gathered.  Had  investigation  remained 
the  method  of  ascertaining  truth,  the  history  of  in- 
tellectual development  would  have  been  far  different. 

The  Arrest  of  Inquiry. — With  the  overthrow  of 
ancient  civilization  the  conditions  of  mental  life  were 
so  altered  that  there  came  about  an  arrest  of  inquiry 
that  bred  ignorance  and  led  to  the  decline  of  science. 
All  independent  observation  ceased.  Men  no  longer 
interrogated  nature  by  the  method  that  had  proved 
so  fruitful.  This  condition  of  human  development 
supplies  an  answer  to  the  question  continually 
raised — "Why  was  there  no  direct  development  of 
learning  on  the  splendid  Greek  foundation? " 

With  the  sweep  of  the  barbarian  hordes  from  the 
north  over  the  civilized  people  of  the  south,  monu- 
ments of  civilization  were  destroyed,  libraries  were 
pillaged  and  burned,  books  became  scarce  and,  subse- 
quently, were  housed  chiefly  in  the.  monasteries. 


46       THE  MAIN  CURRENTS  OF  ZOOLOGY 

General  ignorance  prevailed.  The  means  of  dis- 
semination of  knowledge  did  not  exist,  but  the  chief 
factor  in  the  overthrow  of  learning  was  the  arrest  of 
inquiry  into  natural  phenomena  and  the  substitution 
therefor  of  a  metaphysical  method.  The  priesthood 
had  access  to  the  manuscript  writings,  and  they,  with 
the  medical  men  of  the  period,  became  the  educated 
classes.  Under  these  conditions  the  direction  of 
intellectual  life  was  assumed  by  the  theologians  who 
were  chiefly  interested  in  contemplation  of  the 
spiritual  and  the  supernatural  and  the  medical  men 
were  submerged  by  the  general  change  in  the  in- 
tellectual atmosphere. 

A  world-shunning  spirit  was  engendered  that  was 
hostile  to  scientific  inquiry  and  observations  of  nature 
came  to  be  looked  on  as  prompted  by  impious  cu- 
riosity, and  as  an  attempt  to  pry  into  the  secrets 
of  the  Creator.  Without  the  wholesome  effect  of 
observation  and  experiment,  mystical  explanations 
were  invented  for  natural  phenomena  and  ignorance 
and  superstition  prevailed.  To  question  the  mystical 
interpretations  of  nature  was  to  invite  theological 
persecution.  No  science  could  prosper  under  these 
conditions,  and  zoology  languished  in  common  with 
the  other  sciences. 


ZOOLOGY  EMERGES  47 

A  barren  period  of  intellectual  life  followed.  Al- 
though the  intellectual  life  of  the  middle  ages  was 
active  among  theologians,  philosophers  and  other 
educated  classes  it  was  so  directed  that  for  a  period 
of  a  thousand  years,  under  the  dominance  of  theolog- 
ical authority,  no  really  productive  writings  resulted. 
The  leading  medical  men  kept  alive  some  spirit  of 
investigation  but  it  was  confined  to  then:  own  craft 
and  was  handed  along  by  preceptor  to  pupil  without 
becoming  common  property.  Their  occupation 
brought  them  into  touch  with  natural  phenomena. 
They  knew  the  properties  of  herbs  and  their  effects 
on  the  human  body.  They  became  acquainted  to 
a  limited  degree,  with  anatomy  and  physiology. 
Finally,  it  was  through  the  medical  men  that  renewal 
of  observation  on  organic  nature  was  brought  about. 

Renewal  of  Observation. — Nearly  nineteen  cen- 
turies after  Aristotle  there  occurred,  as  one  of  the 
features  of  the  Renaissance,  a  revival  of  the  scientific 
method  bringing  once  more  into  human  affairs  the 
indispensable  conditions  even  for  the  existence  of 
science.  As  the  decline  of  science  had  been  largely 
due  to  the  arrest  of  inquiry,  and  the  substitution  of 
authority  for  investigation  as  the  method  of  ascer- 
taining truth,  so  the  renewal,  so  far  as  progress  of 


48        THE  MAIN  CURRENTS  OF  ZOOLOGY 

zoology  was  concerned,  was  a  return  to  the  observa- 
tion of  nature. 

This  new  movement  was  a  revolt  of  the  intellect 
against  existing  conditions.  In  its  entirety  it  is 
called  the  Renaissance.  It  was  several  centuries  in 
gaining  enough  headway  to  break  over  the  barriers 
that  had  been  stretched  across  the  path  of  progress. 
From  time  to  tune  the  more  independent  thinkers  and 
the  more  gifted  individuals  had  attempted  to  restore 
the  practice  of  independent  observation  and  thought, 
but,  repeatedly,  their  efforts  were  suppressed  by 
theological  opposition.  Finally,  in  the  sixteenth  cen- 
tury, through  the  efforts  of  men  like  Galileo,  Des- 
cartes and  Vesalius  the  method  of  scientific  investiga- 
tion was  established.  The  renovation  of  intellectual 
life  began  as  early  as  the  thirteenth  century  and 
involved  an  expression  of  the  human  spirit  in  various 
directions — artistic,  literary,  scientific,  etc.  The 
artistic  and  literary  development  preceded  the 
scientific,  and  it  was  not  until  the  Renaissance  was 
well  under  way  that  the  scientific  revival  took  place. 
In  the  latter  was  involved  not  only  the  progress  of 
zoology,  but  all  the  benefits  that  have  accrued  from 
the  development  of  modern  science. 

Among  the  actors  in  the  scientific  renaissance, 


ZOOLOGY  EMERGES  49 

Andreas  Vesalius  (1514-1560),  by  reforming  anatomy 
and  thus  placing  morphological  study  on  a  new  plane, 
stands  closest  related  to  zoology.  His  great  illus- 
trated work  on  the  structure  of  the  human  body 
(De  Fabrica  Humani  Corporis}  1543),  based  entirely 
on  observation,  not  only  restored  anatomy  but  at 
the  same  time  laid  the  foundations  for  the  structural 
studies  of  animals.  On  account  of  the  wide  influence 
of  this  book  of  Vesalius',  published  in  1543,  we  must 
recognize  it  as  one  of  the  milestones  of  biological 
progress.  It  was  his  method  of  direct  investigation 
that  produced  the  greatest  results. 

Previous  to  Vesalius  anatomy  had  been  expounded 
from  the  desk  chiefly  by  readings  from  Galen,  a 
celebrated  physician  of  the  fourth  century  A.  D. 
The  strict  adherence  of  Vesalius  to  observations  and 
faithfully  drawn  sketches  from  actual  dissections 
not  only  corrected  many  of  Galen's  statements  but 
overthrew  authority  as  a  source  of  knowledge  and 
replaced  it  by  observation. 

Some  years  later  (about  1619)  William  Harvey, 
who  is  known  for  his  discovery  of  circulation  of  the 
blood  (1628),  introduced  experimental  observation 
into  scientific  investigation.  Thus  the  method  of 
science  was  reestablished  and,  on  the  basis  of  ob- 


50       THE  MAIN  CURRENTS  OF  ZOOLOGY 

servation  and  experiment,  scientific  knowledge  began 
to  advance. 

The  zoology  of  the  period  was  intermingled  with 
medical  science,  especially  with  anatomy  and  phys- 
iology, and  had  no  recognized  existence  as  an  in- 
dependent subject.  Although  William  Harvey  in- 
vestigated the  structure  of  many  animals,  the 
embryology  of  the  chick  and  of  some  mammals, 
zoology  remained  in  the  iatric  condition  of  union  with 
medicine.  Out  of  this  condition  zoology  emerged,  not 
full  fledged,  but  as  a  small  offshoot  of  the  medical 
sciences. 

It  was  not  long,  however,  in  arriving  at  an  in- 
dependent position  but  the  zoology  of  the  seven- 
teenth and  eighteenth  centuries  had  few  modern 
aspects. 

In  the  early  years  of  the  Renaissance  Aristotle  was 
translated,  and  later  small  independent  advances  were 
made  by  various  writers  as  Wotton  (1552),  Jonston 
(1549-1553)  and  Aldrovandi  (1599-1606).  The  most 
important  zoological  work  between  Aristotle  and 
John  Ray  (the  immediate  prececessor  of  Linnaeus), 
was  that  of  the  Swiss,  Conrad  Gesner  (1516-1565). 
His  Historia  Animalium  is  a  voluminous  publica- 
tion, four  volumes  appearing  between  1551  and  1556, 


ZOOLOGY  EMERGES  51 

and  a  fifth  in  1587,  twenty-two  years  after  his  death. 
In  some  editions  it  contains  4500  folio  pages  and 
nearly  1000  illustrations. 

Through  the  renewal  of  observation  the  stream  of 
science,  so  long  held  in  check  by  wrong  methods,  was 
released,  movement  was  started  and  the  seventeenth 
century  was  notable  .  for  advance  in  independent 
observation.  The  microscope  was  introduced  as  a 
tool  of  investigation.  The  whole  field  of  nature  came 
rapidly  under  examination.  Structural  studies  were 
applied  to  vegetables  as  well  as  to  animals.  Mal- 
pighi  (1628-1694),  Swammerdam  (1637-1680)  and 
Leeuwenhoek  (1632-1723)  investigated  the  structure 
of  insects  and  of  other  simple  animals  producing 
valuable  work  on  minute  anatomy,  on  histology  and 
on  embryology.  To  notice  these  really  important 
contributions  in  detail  would  unduly  prolong  the 
story.  Accordingly,  we  pass  to  Linnaeus  (1707- 
1778)  with  whom  systematic  zoology  may  be  said  to 
have  begun. 


CHAPTER  V 
LINN^US  AND  HIS  INFLUENCE 

THE  service  of  Linnaeus  to  natural  history  was 
unique.  He  introduced  clarity  and  system.  The 
known  animals  and  plants,  ever  increasing  in  number 
through  the  collections  of  travelers  and  naturalists, 
were  in  a  confused  state.  They  were  known  by  local 
names  in  different  sections  of  the  same  country  and 
were  differently  designated  in  various  languages. 
By  adopting  Latin  as  a  uniform  medium  he  elabo- 
rated a  system  of  naming  every  production  of  nature 
in  two  words,  a  generic  and  a  specific  name,  as  Fells 
domesticate)  for  the  domestic  cat  and  Canis  familiaris 
for  the  domesticated  dog.  The  other  members  of  the 
cat  family  as  the  lion,  tiger,  leopard,  etc.,  were  given 
the  generic  name  of  Felis  and  the  specific  name,  in 
each  case,  distinguished  the  particular  kind  of  Felis. 
In  a  like  manner,  the  members  of  the  dog  family  as 
the  wolf,  the  fox,  etc.,  are  of  the  genus  Canis  but  the 
specific  attached  to  the  generic  name  indicates  the 
particular  kind  of  anmal.  The  cat  family  as  a  whole 
was  designated  Felidae  and  the  dog  family  Canidae. 

Thus  we  have  a  simple  and  uniform  system  by 

5* 


LINN^US  AND  HIS  INFLUENCE  53 

which  all  animals  may  be  named.  This  system  was 
adopted  throughout  the  world,  and  by  a  happy  stroke 
Linnaeus  gave  to  natural  science  a  common  language 
that  remains  in  use  to-day.  The  influence  of  this  may 
be  realized  when  we  remember  that  the  naturalists 
of  all  countries  use  identical  names  for  the  same 
animals  and  plants.  He  also  simplified  the  problem 
of  identification  by  giving  terse  descriptions,  involv- 
ing only  the  salient  points  by  which  animals  and 
plants  may  be  recognized. 

His  publication  the  Systema  Natures  which  passed 
through  twelve  editions  (first  edition  in  1735)  is  by 
no  means  a  treatise  on  organization  of  annuals  and 
plants,  but  a  methodically  arranged  catalogue  with 
brief  descriptions  and  their  new  names.  The  Sys- 
tema embraces  also  a  consideration  of  minerals. 

Linnaeus  did  not  invent  the  binomial  nomenclature 
but  brought  it  into  general  use,  and  by  common  con- 
sent, zoologists  accept  as  the  starting  point  for 
zoological  names  the  tenth  edition  of  the  Systema 
Natures  published  in  1758.  The  botanists  frequently 
use  as  a  base  line  for  names  his  Species  Plantarum  of 

1753- 
Although  Linnaeus  made  a  lasting  impression,  he 

gave  to  natural  history  a  one-sided  development. 


54       THE  MAIN  CURRENTS  OF  ZOOLOGY 

His  followers  were  chiefly  collectors  and  classifiers, 
who  by  interminable  species-making  brought  zoology 
into  disrepute  from  which  it  was  rescued  by  Cuvier 
and  others  who  emphasized  structure,  development, 
and  physiology  rather  than  mere  classification.  , 

Linnaeus  also  defined  species,  which  centered  at- 
tention on  the  distinguishing  characters  of  animals, 
and  paved  the  way  for  the  consideration  of  the  origin 
of  species  that  became  so  significant,  under  Darwin 
in  the  nineteenth  century.  In  this  particular  Lin- 
naeus was  preceded  by  John  Ray  (1628-1705)  who 
was  the  first  to  introduce  into  natural  history  an 
exact  conception  of  what  is  species. 

Linnaeus  (Fig.  12)  was  born  in  Rashult,  Sweden, 
1707,  the  son  of  a  poor  Lutheran  pastor.  He  was 
inattentive  to  ordinary  studies,  being  engaged  with 
his  own  thoughts  and  taking  delight  in  collecting 
natural  objects.  He  was  regarded  as  dull  and  un- 
fitted for  an  intellectual  career.  His  father,  in 
dispair,  was  about  to  apprentice  him  to  a  shoemaker 
when  a  doctor  of  the  town  recognized  his  unusual 
type  of  mind  and  pursuaded  his  father  to  promote  his 
education.  After  many  struggles  with  poverty,  he 
was  graduated  from  the  University  of  Hardewyk  in 
Holland  in  1735  with  the  degree  of  Doctor  of  Med- 


FIG.  ii. — ARISTOTLE 
(384-322  B.  C.) 


FIG.  12. — CAROLUS  LIXN.EUS 
(1707-1778) 


FIG.  13. — RUDOLPH  LEUCKART 

(1823-1898) 


FIG.  14. — GEORGES  CUVIER 
(1769-1832) 


LINN^US  AND  HIS  INFLUENCE  55 

icine.  But  he  was  destined  for  a  university  career, 
and  after  a  few  years  of  wandering  in  which  he  visited 
France  and  England,  he  was  appointed  professor  at 
the  University  of  Upsala  and  became  one  of  the  most 
widely  recognized  men  of  its  faculty.  His  drawing 
power  was  great,  during  his  residence  the  attendance 
at  the  University  advanced  from  500  to  1500  and  his 
classes  were  attended  by  several  hundred  students. 
He  sustained  close  personal  relations  with  his  stu- 
dents and  his  teaching  gave  a  great  impetus  to  the 
study  of  natural  history.  His  disciples  were  for  the 
most  part  men  of  smaller  type  and  in  their  hands  the 
study  of  zoology  was  lowered  by  their  devotion  to 
species-making  while  observations  of  a  more  im- 
portant character  on  animals  were  neglected.  Ac- 
cordingly, the  influence  of  Linnaeus  was  not  progres- 
sive. His  chief  service  was  to  reduce  to  systematic 
form  observations  on  the  external  and  general  char- 
acter of  animals  and  to  supply  the  nomenclature  that 
is  in  use  at  the  present  day. 

As  to  personal  appearance  and  human  qualities 
this  light-haired  Swede  was  a  short,  thick  man  with 
large  limbs,  affable  and  easy  of  approach.  He  was 
vain  and  his  self-esteem  was  greatly  increased  by  the 
widely  extended  praise  that  had  been  given  to  his 


56       THE  MAIN  CURRENTS  OF  ZOOLOGY 

work.  He  was  impatient  towards  criticism  and 
adverse  comment  of  his  work  often  threw  him  into  a 
violent  passion. 

In  1907  occurred  the  two  hundredth  anniversary 
of  his  birth  which  was  celebrated  by  the  University  of 
Upsala  with  appropriate  ceremonies.  At  this  time 
many  articles  were  published  about  Linnaeus  that 
supply  abundant  reading  matter  regarding  his  life 
and  work.  To  mark  this  celebration  there  was  pub- 
lished a  facsimile  reproduction  of  the  first  edition  of 
the  Systema  Natures — a  folio  of  eight  pages — con- 
taining the  systematic  arrangement  of  the  "three 
kingdoms  "  of  nature  embracing  minerals,  plants  and 
animals.  This  interesting  document  is  readily  ac- 
cessible in  the  book  market. 

A  splendid  offshoot  of  the  natural  history  of 
Linnaeus  is  Ecology — the  study  of  organisms  in 
relation  to  their  surroundings.  This  has  wider 
affinities  but  is  related  to  natural  history.  For  con- 
venience we  may  also  place  in  this  wide  territory  the 
Geographical  Distribution  of  Animals. 

The  Linnaean  system  of  classification  had  grave 
defects.  It  was  not  founded  on  a  knowledge  of  the 
comparative  structure  of  animals  and  plants,  but  in 
many  instances  upon  superficial  features  that  were 


LIN1SLEUS  AND  HIS  INFLUENCE  57 

not  distinctive  in  determining  their  position  and 
relationships.  His  system  was  essentially  an  arti- 
ficial one,  a  convenient  key  for  finding  the  names  of 
animals  and  plants,  but  doing  violence  to  the 
natural  arrangement  of  those  organisms. 

To  do  justice,  however,  to  the  discernment  of 
Linnaeus,  it  should  be  added  that  he  was  fully  aware 
of  the  artificial  nature  of  his  classification.  A  real 
natural  system,  founded  on  the  true  affinities  of 
animals  and  plants  as  indicated  by  their  structural 
characters,  he  regarded  as  the  highest  ami  of  classifi- 
cation. But,  he  never  completed  a  natural  system, 
learning  only  a  fragment. 

Even  the  larger  groups  of  animals  were  extended 
and  much  modified  by  Cuvier,  by  von  Siebold,  by 
Leuckart  and  by  others.  As  to  the  larger  divisions 
of  animals  and  plants,  Linnaeus  recognized  only 
classes  and  orders.  Then  came  genera  and  species. 
He  did  not  use  the  term  family  in  his  formulae;  this 
convenient  designation  having  been  introduced,  in 
1780,  by  Batch. 

The  first  modification  of  importance  to  the  Lin- 
naean  system  was  that  of  Cuvier,  who  proposed 
(1815)  a  grouping  of  animals  based  upon  a  knowledge 
of  their  comparative  anatomy.  He  declared  that 


58       THE  MAIN  CURRENTS  OF  ZOOLOGY 

animals  exhibit  four  types  of  organization  (Verte- 
brata,  Mollusca,  Articulata  and  Radiata)  and  his 
types  were  substituted  for  the  primary  groups  of 
Linnaeus. 

But  naturalists  were  not  long  in  discovering  that 
the  primary  divisions  of  Cuvier  were  not  well  bal- 
anced, and,  indeed,  that  they  were  not  natural 
divisions  of  the  animal  kingdom. 

The  group  Radiata  was  the  least  sharply  denned, 
since  Cuvier  had  included  in  it  not  only  those  animals 
which  exhibit  a  radial  arrangement  of  parts,  but  also 
unicellular  animals  that  were  asymmetrical,  and 
some  of  the  worms  that  showed  bilateral  symmetry. 
Accordingly,  Karl  Th.  von  Siebold,  in  1845  separated 
these  animals  and  redistributed  them.  For  the 
simplest  unicellular  animals  he  adopted  the  name 
Protozoa,  which  they  still  retain,  and  the  truly 
radiated  forms,  as  starfish,  sea-urchins,  hydroid 
polyps,  coral  animals,  etc.,  were  united  in  the  group 
Zoophyta.  Von  Siebold  also  changed  Cuvier's 
branch,  Articulata,  separating  those  forms,  such  as 
Crustacea,  insects,  spiders,  and  myriopods,  which 
have  jointed  appendages,  into  a  natural  group  called 
Arthropoda,  and  uniting  the  segmented  worms  with 
those  worms  that  Cuvier  had  included  in  the  radiate 


LINNAEUS  AND  HIS  INFLUENCE  59 

group,  into  another  branch  called  Vermes.  This 
separation  of  the  four  original  branches  of  Cuvier 
was  a  movement  in  the  right  direction,  and  was 
destined  to  be  carried  still  farther. 

Rudolph  Leuckart  (Fig.  13),  the  distinguished 
zoologist  of  Leipsic,  following  the  lead  of  von  Siebold 
made  further  modifications.  He  split  von  Siebold's 
group  of  Zoophytes  into  two  distinct  kinds  of  radiated 
animals:  the  starfish,  sea-urchins,  sea-cucumbers, 
etc.,  having  a  spiny  skin,  he  designated  Echinoderma; 
the  jelly-fishes,  polyps,  coral  animals,  etc.,  not  posses- 
sing a  true  body  cavity,  were  also  united  into  a 
natural  group,  for  which  he  proposed  the  name 
Ccelenterata. 

From  all  these  changes  there  resulted  the  seven 
primary  divisions — branches,  subkingdoms,  or 
phyla — which  with  small  modifications  are  still  in 
use.  These  are  Protozoa,  Ccelenterata,  Echino- 
derma, Vermes,  Arthropoda,  Mollusca,  Vertebrata. 
These  seven  phyla  are  not  entirely  satisfactory  and 
there  has  resulted  from  more  careful  analysis  a 
multiplication  of  subkingdoms  and  a  redistribution 
of  forms  as  in  the  case  of  the  brachiopods,  the 
sponges,  the  tunicates,  etc. 

A  tabular  view  showing  the  modifications  made  in 


60       THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  larger  groups  of  animals  will  be  helpful  at  this 
point. 


LINNAEUS 
Mammalia  (Mammals) 

Aves  (Birds) 

Amphibia  (Amphibia 
and  Reptiles) 
Pisces  (Fishes) 
Insecta  (Including 
Crustacea,  etc.) 
Vermes  (Including 

CUVIER 

Vertebrata  (Embracing 
five    classes:    Mam- 
malia,   Aves,     Rep- 

tilia    Batrachia    Pis- 
ces) 

Mollusca 
Articulata 

VON  SIEBOLD 

Vertebrata 
(Embrac- 
ing five 
classes) 

Mollusca 
f  Arthropoda 

LEUCKAR 

Vertebrata 
(Five 
classes) 

Mollusca 
Arthropoda 

Mollusca  and  all 
lower  forms) 

Radiata  

\  Vermes 
f  Zoophyta 

Vermes 

f  Echinodei 
\  Ccelenter; 

I  Protozoa 

Protozoa 

Biological  progress  (outside  the  changes  in  classi- 
fication) from  Linnaeus  to  Darwin,  although  details 
were  greatly  multiplied,  proceeded  by  definite  steps. 
Linnaeus  and  his  successors  were  concerned  with  the 
organism  as  a  whole,  the  external  appearance,  colors, 
spots,  the  horns,  the  hoofs,  etc.  The  next  distinct 
step  was  that  taken  by  Cuvier  and  his  school.  In- 
stead of  the  complete  organism,  the  organs  of  which 
it  is  composed  became  the  chief  subject  of  analysis. 
The  organism  was  dissected,  the  organs  were  exam- 
ined and  those  of  one  kind  of  animal  were  compared 
with  another.  This  started  the  line  of  comparative 
anatomy  which  played  a  much  more  important  part 
in  the  development  of  zoology  than  work  of  the 
Linnaean  type.  After  the  organs  were  investigated 
the  tissues  came  under  review  and,  then,  with  more 


LINNJEUS  AND  HIS  INFLUENCE  61 

incisive  inquiry,  the  cells  composing  the  tissues 
became  the  object  of  investigation.  These  progres- 
sive steps  of  analysis,  from  the  organism,  to  organs, 
to  tissues  and  cells  finally  culminated  in  the  recogni- 
tion of  protoplasm  the  actually  living  substance  of 
all  animal  (and  plant)  organization. 

Knowledge  of  the  physiological  side  of  animal  life 
had  a  parallel  development.  In  the  period  of  Lin- 
naeus, the  physiology  of  the  organism  was  pursued 
by  Haller  and  his  school;  following  this  the  physiol- 
ogy of  organs  and  tissues  was  advanced  by  J.  Muller, 
Bichat  and  others.  Later,  Virchow  investigated  the 
physiology  of  cells,  and  Claude  Bernard  the  chemical 
activities  of  protoplasm. 


CHAPTER  VI 
CUVIER  AND  STRUCTURAL  ZOOLOGY 

AFTER  Linnaeus  had  founded  natural  history  and 
started  activity  in  collecting  and  classifying  animals 
zoology  was  soon  in  ripe  condition  for  a  new  depar- 
ture. The  method  of  Linnaeus  brought  about  a 
general  familiarity  with  the  animal  kingdom,  but  so 
long  as  studies  were  confined  to  externals  and  to  the 
organism  as  a  whole  no  deep-seated  advance  could 
be  made. 

Cuvier  now  came  forward,  and  by  a  more  incisive 
analysis,  he  placed  emphasis  on  the  study  of  struc- 
ture as  the  key  to  the  knowledge  of  animal  life. 
When  structure  is  pursued  to  its  limit,  by  embracing 
microscopic  as  well  as  gross  anatomy  and  the  process 
of  development,  it  makes  a  very  important  division  of 
zoological  study.  This  is  structural  zoology  or  com- 
parative anatomy.  The  combination  of  the  various 
studies  that  fall  under  this  head  are  commonly 
designated  morphological  studies  and  the  term 
morphology  is  used  to  embrace  them  all. 

In  order  to  complete  the  picture  of  animal  life 

there   is   needed    the    complementary    division    of 

62 


CUVIER  AND  STRUCTURAL  ZOOLOGY      63 

physiological  studies.  Thus  Physiology  and  Mor- 
phology are  the  two  chief  divisions  of  Zoology.  We 
must  remember  that  there  was  concurrent  progress 
in  these  two  departments  but  for  clearness  they  must 
be  separately  considered. 

Cuvier  (1767-1832),  (Fig.  14),  although  he  had  his 
forerunners,  may  be  said  to  have  founded  compara- 
tive anatomy  about  1805,  and  his  influence  dom- 
inated zoology  for  the  first  third  of  the  nineteenth 
century.  After  attendance  at  the  Carolinian  Acad- 
emy, at  Stuttgart,  in  order  to  add  to  his  slender 
purse,  he  accepted  employment  as  private  tutor  to 
the  sons  of  the  Count  d'H6ricy.  This  took  him  to 
the  sea  coast  near  Caen  in  northern  France.  Hav- 
ing time  at  his  disposal,  with  eager  enthusiasm  he  set 
himself  to  become  acquainted  with  the  structure  of 
marine  animals  (especially  mollusca).  The  results 
of  his  investigations  were  sent  to  Paris  for  publica- 
tion and  this  served  to  bring  him  to  the  notice  of  the 
working  naturalists  of  the  French  metropolis.  In 
particular,  Lamarck  and  Geoffroy  Saint-Hilaire  con- 
nected with  the  Royal  Garden  (Jardin  du  Roi,  later 
the  Jardin  des  Plantes)  gave  a  hospitable  reception  to 
his  work  and  extended  a  helping  hand.  He  was 
invited  to  come  to  Paris  to  connect  himself  with  the 


64       THE  MAIN  CURRENTS  OF  ZOOLOGY 

Jardin  du  Roi,  and  here  he  developed  the  Natural 
History  Museum  and  gained  recognition.  Paris  was 
thereafter  his  home  and  the  scene  of  his  triumphs. 

His  was  an  attractive  personality  and  as  he  threw 
himself  into  his  work  with  enthusiasm  and  well- 
directed  industry,  he  gained  power,  and  soon  forged 
ahead  of  his  companions  in  research.  He  was  a 
favorite  of  the  Emperor  Napoleon  and  by  him  was 
made  head  of  the  educational  system  of  France.  He 
became  a  legislator  and,  finally,  a  Peer  of  France, 
but  with  all  his  public  duties  he  remained  faithful  to 
his  love  of  zoological  science  and  continued  to  work 
in  that  field. 

After  his  extensive  treatise  on  comparative  anat- 
omy (1805)  he  published,  in  1815,  his  well-known 
book  on  the  Animal  Kingdom  (Le  Regne  Animal). 
In  this  he  divided  the  animal  kingdom  into  branches 
(embranchements)  on  the  basis  of  their  structure, 
recognizing  as  stated  in  the  previous  chapter,  four 
great  types  of  structure,  the  radiate,  articulate, 
molluscan  and  vertebrate.  Although  this  classifica- 
tion has  been  superseded  by  a  better  one,  the  basis  of 
structure  employed  by  Cuvier  was  important  and  was 
used  in  further  advances. 

Comprehensiveness  of  view  was  a  distinguishing 


CUVIER  AND  STRUCTURAL  ZOOLOGY      65 

feature  of  Cuvier's  mind.  In  his  investigations  he 
covered  the  whole  field  of  animal  organization  from 
the  lowest  to  the  highest,  and  combining  his  results 
with  what  had  been  accomplished  by  earlier  workers, 
he  established  comparative  anatomy  on  broad  lines 
as  an  independent  branch  of  natural  science. 

Cuvier  represents  the  beginning  of  that  side  of 
zoology  that  reached  its  highest  development  in 
Karl  Gegenbaur  (1826-1903)  and  Max  Ftlrbringer  of 
Germany,  in  Owen  (1804-1892)  and  Huxley  (1825- 
1895)  of  Great  Britain,  and  in  Joseph  Leidy  (1823- 
1891)  and  E.  D.  Cope  (1840-1897)  of  the  United 
States.  His  intellectual  heirs  in  France  were  H. 
Milne-Edwards  (1800-1885)  and  Lacaze-Duthiers 
(1821-1901). 

Notwithstanding  all  his  mental  gifts,  Cuvier  was 
not  able  to  appreciate  the  most  important  contribu- 
tion made  to  zoology  in  his  period,  by  his  distin- 
guished contemporary  and  fellow-worker,  Lamarck. 
He  became  a  strong  opponent  of  the  theory  of  organic 
evolution  of  which  Lamarck  was  the  founder  (1801 
and  1809)  in  its  modern  sense.  How  completely 
Cuvier's  opposition  served  to  hold  in  check  the 
progress  of  this  fruitful  idea  in  France  is  well  recog- 
nized. 


66       THE  MAIN  CURRENTS  OF  ZOOLOGY 

His  famous  debate  with  Saint-Hilaire,  in  1830,  on 
the  subject  of  unity  of  type  involved  the  principles  of 
evolution.  Cuvier  won  the  debate  largely  from  skill 
as  a  debater  and  his  personal  magnetism.  Posterity 
views  the  matter  in  a  different  light  and  reckons  this 
opposition  to  Lamarck's  views  as  one  of  the  short- 
comings of  Cuvier. 

His  influence  was  so  lasting  that  it  prevented  for 
many  years  a  respectful  hearing  of  the  evolutionary 
idea  in  France,  and  she  was  the  last  of  the  highly 
intellectual  nations  to  harbor  as  true  the  ideas  of 
organic  evolution.  Frenchmen,  however,  have  at- 
toned  for  this  to  a  degree  by  establishing  in  the 
University  of  Paris  a  Professorship  of  Evolution 
under  the  charge  of  Maurice  Caullery,  and  have 
given  a  cordial,  if  somewhat  belated,  recognition  to 
one  of  their  foremost  zoologists — Lamarck. 

Comparative  anatomy,  the  subject  founded  by 
Cuvier,  supplies  some  of  the  most  obvious  and  con- 
vincing evidences  of  organic  evolution.  Rightly 
pursued  it  is  a  rich  subject  not  only  for  facts  but  for 
ideas.  It  is  the  division  of  zoology  most  commonly 
used  in  the  laboratory  exercises  of  the  present  time. 

Before  leaving  the  consideration  of  Cuvier's  con- 
tribution to  zoology,  it  should  be  pointed  out  that  he 


CUVIER  AND  STRUCTURAL  ZOOLOGY      67 

recognized  the  fossil  vertebrates  of  the  Paris  basin  as 
being  the  remains  of  extinct  animals,  and  he  founded 
the  science  of  vertebrate  paleontology.  Lamarck, 
whose  researches  were  largely  directed  to  the 
analysis  of  the  invertebrates,  also  investigated  the 
fossil  remains  of  these  lower  animals  and  founded 
invertebrate  paleontology. 

As  we  shall  see  in  a  future  chapter  the  investigation 
of  fossil  remains  is  a  part  of  zoological  study. 

Histology. — The  structure  of  organisms  presents 
two  phases,  that  which  is  discernible  to  the  unaided 
eye  and  that  revealed  only  by  the  microscope.  The 
former  is  gross  anatomy  and  the  latter  rninute  or 
microscopic  anatomy.  The  study  of  the  micro- 
scopic structure  of  the  tissues  is  so  important  and 
offers  so  many  problems,  that  a  new  division  of  struc- 
tural zoology  (comparative  anatomy)  arose  under  the 
name  of  histology. 

This  is  the  microscopic  anatomy  of  the  tissues. 
The  brilliant  Bichat  (1771-1801)  was  a  pioneer  in  the 
investigation  of  the  tissues  of  animals  but  histology 
did  not  take  form  until  later.  The  establishment  of 
the  cell- theory  in  1839  gave  a  great  impetus  to  this 
study,  and  histology  in  the  hands  of  Goodsir,  of  Eng- 
land, Koelliker,  of  Germany,  and  Ranvier,  of  France, 


68       THE  MAIN  CURRENTS  OF  ZOOLOGY 

took  on  new  and  important  aspects.  It  is  a  subject 
in  which  all  medical  students  are  trained  and  reveals 
what  may  be  called  the  physiological  anatomy  of  the 
tissues.  After  the  establishment  of  the  cell-theory 
it  became  clear  that  organs  do  not  perform  their 
function  as  units  but  through  their  smaller  ele- 
ments— the  cells. 

The  rise  of  histology  is  interesting,  but  to  follow  it 
specifically  would  involve  too  great  detail.  Among 
the  many  workers  in  this  field  we  may  select  von 
Koelliker  (1817-1905),  (Fig.  15),  as  the  typical 
histologist  of  the  nineteenth  century.  He  published 
a  text-book  of  Histology  in  1857  and,  thereafter,  for 
forty  years  he  continued  to  make  contributions  to 
this  division  of  science.  His  great  book  on  the  tissues 
(Handbuch  der  Gewebelehre)  passed  through  several 
editions  from  1870  to  1897.  It  was  thoroughly  revised 
and  brought  down  to  date  in  the  years  1894-1897. 

The  plant  histologists,  Grew  and  Malpighi,  of  the 
eighteenth  century  made  interesting  observations 
and  published  many  sketches  of  the  microscopic  ap- 
pearance of  plant  tissues.  These  sketches,  which 
were  faint  foreshadowings  of  the  cell  idea,  can  be 
examined  by  those  sufficiently  interested  to  look 
up  the  works  of  Grew  and  Malpighi. 


CUVIER  AND  STRUCTURAL  ZOOLOGY      69 

Leydig  (1821-1908),  in  1864,  applied  histology  to 
insects  and  other  invertebrates. 

Virchow  developed  a  line  of  abnormal  histology 
which  figures  now  under  the  name  Pathology.  Thus 
structural  studies  of  the  tissues  under  the  microscope 
have  given  rise  to  normal  histology  and  abnormal 
(pathological)  histology  or  pathology. 


CHAPTER  VII 
THE  RISE  OF  EMBRYOLOGY 

AFTER  the  comparative  anatomy  of  Cuvier  was 
well  under  way  came  the  establishment  of  embryol- 
ogy in  which  von  Baer  (1797-1876)  was  the  central 
figure.  In  1828,  by  the  publication  of  his  detailed 
observations  on  the  development  of  the  chick  and 
other  animals  (1834),  he  established  the  germ-layer 
idea  and  carried  the  science  of  the  development  of 
animals  to  a  high  level. 

Embryology  is  supplemental  to  comparative  anat- 
omy and  in  its  present  stage  of  development  is  to  be 
classified  as  a  morphological  subject.  It  is  not  pos- 
sible to  appreciate  in  its  full  meaning  any  structural 
problem  of  zoology  without  the  assistance  of  em- 
bryological  study.  The  adult  condition  of  an  or- 
ganism is  the  result  of  a  series  of  changes,  it  is,  in 
fact,  the  last  step  in  a  long  series  of  modifications 
that  have  occurred  in  the  process  of  building  the 
body  from  the  single-celled  condition  of  the  egg  to  its 
completed  state.  These  modifications  are  so  pro- 
found that  often  the  affinities  of  the  animal  can- 
not be  recognized  in  the  modified  state,  and  we 

70 


THE  RISE  OF  EMBRYOLOGY  71 

must  go  backwards  and  follow  the  embryological 
record  to  see  where  the  modifications  of  structure 
occurred. 

The  most  unexpected  and  most  illuminating  expe- 
riences come  from  this  source.  In  the  embryos  of 
higher  animals  are  found  many  traces  of  former 
ancestral  conditions.  Evanescent  organs  as  gill- 
slits  (with  appropriate  circulation)  occur  in  all  higher 
animals  including  the  human  body.  The  gill-slits  of 
birds  and  mammals  are  transient  and  never  come  to 
functional  use.  But  their  presence  is  indubitable, 
and  we  begin  to  realize  that  they  are  clues  to  the 
structural  features  of  ancestral  forms.  They  have 
been  handed  along  by  heredity  and  although  not 
rising  to  a  functional  condition,  they  exist  as  hered- 
itary survivals  from  the  days  when  the  ancestors  of 
birds  and  mammals  were  aquatic  and  had  use  for 
gill-slits  in  respiration.  The  presence  of  rudimentary 
teeth  hi  the  jaws  of  the  embryos  of  toothless  whales 
have  the  same  significance. 

Besides  the  transitory  hereditary  survivals,  there 
are  many  rudimentary  organs  such  as  rudimentary 
ear  muscles,  tail  muscles  and  the  vermiform  appendix 
of  the  human  body  which  are  interpreted  in  a  similar 
way. 


72       THE  MAIN  CURRENTS  OF  ZOOLOGY 

It  becomes  apparent,  that  in  the  course  of  develop- 
ment there  is  an  embryological  record  impressed 
upon  the  organism,  embryological  study  reveals  this 
record  and  its  interpretation  is  part  of  the  task  of  the 
anatomist.  Embryology  is  of  great  importance  in 
zoology  as  giving  clues  to  the  relationship  of  animals 
and  affording  data  for  the  recognition  of  their  line  of 
descent. 

Von  Baer  (Fig.  16),  the  founder  of  modern  em- 
bryology, was  a  man  of  superb  mental  endowment, 
unusual  in  the  way  in  which  he  combined  accurate 
observations  with  sane  and  fruitful  generalizations. 
His  "reflections"  on  the  general  features  of  the 
development  of  animals  are  still  of  value.  His  book 
on  The  Development  of  Animals  (Entwickelungs- 
geschichte  der  Tiere-Beobachtung  und  Reflexion)  is  one 
of  the  great  biological  classics.  He  had  finished  his 
embryological  investigations  in  1828,  at  the  age  of 
thirty-one,  and  lived  thereafter  for  forty-eight  years. 
At  the  time  of  the  publication  of  his  treatise  on 
embryology  he  was  a  professor  in  the  University  of 
Konigsberg,  but  soon  retired  to  look  after  his  estates 
in  Russia.  He  made  no  further  contributions  to 
embryology  but  became  known  for  investigations  in 
meteorology,  anthropology,  etc.  An  autobiography, 


FIG.  15. — ALBRECHT  VON  KOELLIKER 
(1817-1905) 


FIG.  16. — KARL  ERNST  VON  BAER 

(1792-1876) 


FIG.  17. — FRANCIS  M.  BALFOUR 
(1851-1882) 


FIG.  1 8. — CLAUDE  BERNARD 

(1813-1878) 


THE  RISE  OF  EMBRYOLOGY  73 

published  in  1864,  gives  an  interesting  account  of 
his  mental  development. 

Between  von  Baer  and  Balfour  (1851-1882)  under 
whom  embryology  took  on  modern  aspects,  the 
observations  on  the  development  of  animals  were 
greatly  multiplied.  Activity  was  increased  after  the 
announcement  of  the  cell- theory  (1839)  and  em- 
bryologists  began  to  see  more  clearly  the  significance 
of  the  germinal  elements  and  the  germ-layers. 

It  was  determined  that  the  egg  and  the  sperm  are 
single  cells,  the  final  step  in  reference  to  all  eggs 
being  taken  by  Gegenbaur  in  1865.  The  three  germ- 
layers  common  to  all  animals  above  the  Ccelenterates 
(Hydra,  Hydroids,  Jelly-fish,  etc.)  were  shown  to  be 
essentially  alike  as  to  origin  and  to  give  rise  to  the 
same  kind  of  tissues  in  the  different  animals.  In  the 
light  of  embryology,  all  animals  were  seen  to  be 
related  through  ancestral  lines  and  to  be  united  on  the 
broad  plane  of  similarity  of  origin  and  development. 
Von  Baer  had  already  indicated  this,  but  it  was  in  the 
period  between  him  and  Balfour,  that  this  great 
truth  became  better  illustrated  and  took  hold  on  the 
minds  of  embryologists  and  influenced  their  in- 
vestigations. 

Balfour  (Fig.  17)  now  comes  upon  the  scene  and 


74       THE  MAIN  CURRENTS  OF  ZOOLOGY 

does  eminent  service.  Up  to  this  time  the  investiga- 
tions of  the  embryology  of  animals,  Both  inverte- 
brates and  vertebrates,  had  resulted  in  a  vast  ac- 
cumulation of  monographs  and  scientific  memoirs. 
These  publications  were  scattered  in  technical 
periodicals,  in  the  special  publications  of  learned 
societies,  etc. 

Balfour  gathered  these  researches,  read,  digested 
and  published  the  results  in  a  unified  picture  of  the 
science  of  embryology.  He  clarified  as  well  as 
unified  the  subject  and  produced  a  comprehensive 
book  on  comparative  embryology  that  contained  the 
substance  of  what  was  known  regarding  the  develop- 
ment of  all  animals  from  the  lowest  to  the  highest. 
Balfour  was  especially  gifted  with  the  power  of  dis- 
criminating analysis  and  charm  of  expression.  His 
book,  of  priceless  value  to  embryologists,  was  pub- 
lished in  two  volumes,  1880-1881,  under  the  title  of 
Comparative  Embryology. 

Just  after  completing  this  monumental  work  while 
on  a  journey  to  the  Alps  for  recuperation  he  met  his 
death  by  slipping  with  his  guide  from  one  of  the 
Alpine  passes. 

Since  1881  the  science  of  embryology  has  devel- 
oped rapidly.  There  has  been  great  refinement  of 


THE  RISE  OF  EMBRYOLOGY  75 

observation  and  of  technique.  Studies  have  become 
more  intensive  such  as  following  the  cell-succession 
from  the  egg  step  by  step  until  the  germ-layers  are 
established,  further  investigations  into  the  mech- 
anism of  development,  the  nature  of  fertilization 
and  the  study  of  the  behavior  of  the  chromosomes  of 
egg  and  sperm.  The  subject  has  also  become  ex- 
perimental. 

It  has  become  too  vast  for  a  single  publication  to 
embrace  the  embryology  of  invertebrates  and  verte- 
brates, and,  as  a  consequence,  we  have  the  standard 
embryology  of  invertebrates  by  Korschelt  and  Heider 
and  many  volumes  on  vertebrate  embryology.  There 
are  also  those  on  a  single  animal,  as  Lillie's  Develop- 
ment of  the  Chick,  and  those  on  the  development  of  the 
Human  Body  such  as  the  volumes  by  McMurrich, 
Keibel  and  Mall,  etc. 

The  great  reference  book  on  vertebrate  embryology 
as  a  whole  is  the  comparative  and  experimental 
embryology  of  Vertebrates,  in  six  volumes,  under  the 
editorship  of  Oskar  Hertwig,  assisted  by  a  large 
number  of  collaborators. 

Among  living  and  recent  embryologists  should  be 
mentioned:  Oskar  Hertwig  (b.  1849)  °f  Berlin;  Wil- 
helm  His  (1831-1904)  of  Leipsic,  whose  researches  on 


76       THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  development  of  the  nervous  system,  the  origin  of 
nerve  fibers  and  the  embryology  of  the  human  body 
are  important;  and  the  late  Charles  Sedgwick  Minot 
(1852-1914)  (Fig.  22).  The  last  named  biologist,  of 
dignified  yet  gracious  personality,  is  remembered  for 
the  wide  and  stimulating  influence  which  he  exerted 
upon  the  development  of  biological  research  in  the 
United  States.  He  was  a  prolific  writer,  his  best 
known  books  being  Human  Embryology  and  A  Text 
Book  of  Embryology,  which  take  high  rank.  He 
established  at  the  Harvard  Medical  School  a  com- 
prehensive collection  of  prepared  sections  of  the 
embryos  of  all  classes  of  vertebrate  animals.  Under 
the  name  of  the  Harvard  Collection  these  are  gen- 
erously placed  at  the  service  of  investigators  and 
have  been  the  source  of  sketches  for  a  large  number 
of  embryological  papers. 

The  notable  collection  of  human  embryos  accumu- 
lated on  the  Carnegie  foundation  by  Professor 
Franklin  P.  Mall  (1862-1917),  of  John  Hopkins 
University  is  also  available  for  reference  and  for  the 
use  of  investigators. 


CHAPTER  VHI 

GENERAL   PHYSIOLOGY   AS   A   DIVISION   OF 
ZOOLOGY 

THE  study  of  structure  and  development  is  not 
enough  to  acquaint  us  with  the  essential  features  of 
an  animal.  The  most  significant  thing  about  animal 
mechanism  is  that  it  is  endowed  with  life  and  we 
should  observe  the  principal  activities  of  the  mech- 
anism along  with  its  structure.  As  before  indi- 
cated, morphology  and  physiology  represent  the  main 
divisions  of  zoology.  While  physiology  as  a  science 
has  advanced  to  great  proportions  and  to  a  position 
of  independence,  nevertheless  general  physiology  of 
animals  is  a  part  of  zoology.  It  will,  therefore,  be 
appropriate  at  this  point  to  engage  in  a  considera- 
tion of  the  rise  of  physiology  without  attempting  to 
separate  general  physiology  of  animals  from  the  main 
current. 

Morphology  and  physiology  had  a  parallel  devel- 
opment. Just  as  Vesalius  renovated  structural 
studies  so  Harvey  by  demonstrating  the  circulation 
of  the  blood  gave  life  to  a  new  physiology. 

This  demonstration  of  the  circulation  had  more 

77 


78       THE  MAIN  CURRENTS  OF  ZOOLOGY 

far-reaching  consequences  than  appear  on  the  sur- 
face. It  was  not  merely  showing  that  the  blood 
moves  in  a  circuit,  it  also  opened  up  the  entire  ques- 
tion of  the  part  played  by  the  blood  in  the  animal 
economy.  This  is  basal  to  the  understanding  of 
physiology. 

The  tissues  are  bathed  by  the  blood  current.  It  is 
the  carrier  of  oxygen  to  the  tissues  of  the  body;  into 
its  stream  are  diffused  all  the  products  of  digestion,  of 
secretion,  and  of  excretion;  by  its  circulation  it 
distributes  nourishment  to  the  most  remote  parts  of 
the  body  and  brings  back  the  products  of  worn  out 
tissues  for  elimination  by  the  kidneys,  the  lungs  and 
the  skin.  Accordingly,  a  proper  conception  of  the 
circulation  was  a  necessary  preliminary  for  the  prog- 
ress of  physiology. 

The  classic  book  of  Harvey  (Fig.  30)  on  the  cir- 
culation of  the  blood  (De  Motu  Cordis  et  Sanguinis) 
was  published  in  1628,  but  he  had  been  giving  the 
substance  of  it  in  his  university  lectures  since  1619. 

In  the  time  of  Harvey,  however,  physiology  had 
not  fully  emerged— it  was  still  intermingled  with 
medical  studies.  It  was  not  till  the  following  cen- 
tury, through  the  work  of  Haller,  that  it  took  its 
place  as  an  independent  subject  to  be  pursued  for  its 


GENERAL  PHYSIOLOGY  79 

own  sake  and  not  necessarily  for  its  applications  to 
medicine. 

Haller's  elements  of  physiology  (Elementa  Phys- 
iologies) published  in  1758  was  the  first  comprehen- 
sive treatise  devoted  exclusively  to  that  subject. 
After  Haller  physiology,  now  opened  for  investiga- 
tion, grew  rapidly.  We  must  remember,  however, 
that  Harvey  was  the  pioneer  who  introduced  experi- 
mental study  into  biological  science.  The  work  of 
Haller  greatly  broadened  the  field  and  encouraged 
physiological  experimentation. 

From  the  time  of  Haller  we  pass  to  the  nineteenth 
century.  In  the  opening  year  of  that  century  was 
born  a  man,  Johannes  M tiller,  who  exercised  great 
influence  not  only  on  physiology  but  upon  the  whole 
field  of  biological  science.  Verworn  says  of  him: 
"He  is  one  of  those  monumental  figures  that  the 
history  of  every  science  brings  forth  but  once.  They 
change  the  whole  aspect  of  the  field  in  which  they 
work,  and  all  later  work  is  influenced  by  their 
labors."  Although  Muller  was  professor  of  Phys- 
iology at  Bonn,  and  later  at  Berlin/he  was  also  an 
anatomist  and,  perhaps,  more  of  a  morphologist  .in 
his  methods  of  investigation  than  physiologist.  He 
was  great  in  his  general  influence.  He  had  an  un- 


80       THE  MAIN  CURRENTS  OF  ZOOLOGY 

usual  faculty  for  inspiring  enthusiasm  in  his  students 
and  many  of  them,  as  Helmholtz  and  others,  have 
borne  testimony  of  his  immense  influence  in  giving 
them  an  outlook  on  life  and  inspiring  them  to  their 
highest  endeavor. 

Miiller  (1801-1857)  (Fig.  19)  made  physiology 
broadly  comparative.  He  brought  into  it  all  the 
means  of  advancing  the  knowledge  of  animal  or- 
ganization— morphology,  the  microscope,  chemis- 
try, experiment,  etc.  He  included  psychology  as  a 
new  departure  in  the  study  of  physiology. 

But  to  the  Frenchman  Claude  Bernard  (1813- 
1878)  belongs  the  chief  credit  as  the  innovator  of 
experimental  physiology.  With  the  exception  of 
Ludwig,  no  other  physiologist  of  his  period  can  be 
compared  with  him  in  the  experimental  field.  In  his 
Introduction  to  the  Study  of  Experimental  Medicine 
(Introduction  a  V  etude  de  la  Medecine  Experimentale — 
1865),  ne  summed  up  what  he  had  for  years  been 
teaching  in  his  university  lectures,  and  this  remains 
the  standard  contribution  on  the  aims  and  methods 
of  experimental  physiology. 

Bernard's  position  in  the  history  of  physiology  has 
not  been  fully  appreciated  by  biologists.  He  was  the 
foremost  representative  of  physiology  of  his  period. 


FIG.  19. — JOHANNES  MULLER  (1801-1858) 


GENERAL  PHYSIOLOGY  81 

Notwithstanding  the  overshadowing  figure  of  M  tiller 
and  his  tremendous  general  influence,  Bernard's 
scientific  contributions  to  physiology  are  of  a  higher 
order.  A  careful  reading  of  Bernard's  investigations 
and  lectures  are  serving  to  advance  him  into  the 
foremost  rank.  Although  his  great  skill  as  an  exper- 
imenter and  his  exposition  of  experimental  phys- 
iology in  his  Introduction  entitle  him  to  eminence,  he 
will  be  longest  remembered  for  several  epoch-making 
discoveries. 

Of  these  discoveries  only  two  will  be  mentioned. 
First  the  discovery  of  the  occurrence  of  glycogen  in 
the  liver — one  of  the  first  and  most  complete  studies 
of  internal  secretions.  That  the  liver  forms  animal 
starch  (glycogen)  as  well  as  bile  was  a  brilliant  con- 
clusion which  was  demonstrated  by  well  thought-out 
experiments.  Bernard  was  notable  for  the  way  in 
which  he  directed  his  experiments  towards  definite 
ends.  He  was  no  blind  experimenter  who  reached 
into  the  unknown  by  tentative  gropings,  but  first  he 
made  a  crucial  mental  analysis  of  his  problem,  and 
then  devised  experiments  for  its  investigation. 

His  discovery  of  vaso-motor  nerves — both  dilators 
and  constrictors — was  another  piece  of  experimenta- 
tion of  broad  application  in  physiology. 


82       THE  MAIN  CURRENTS  OF  ZOOLOGY 

It  will  clear  matters  to  remember  that  Bernard 
used  the  designation  experimental  medicine  as 
synonymous  with  physiology,  accordingly  his  Intro- 
duction a  r  etude  de  la  Medecine  experimentale  was  a 
treatise  on  experimental  physiology. 

It  was  Bernard  (Fig.  18)  who  also  gave  a  definite 
position  to  general  physiology  which,  as  before 
stated,  is  a  division  of  biological  study.  His  now 
classic  Phenomena  Common  to  Animals  and  Plants 
(Legons  sur  les  phenomenes  communs  aux  Animaux  et 
aux  Vegetaux),  published  in  1878,  was  the  first 
treatise  devoted  to  consideration  of  the  vital  ac- 
tivities of  plants  and  animals. 

Physiology  established  on  the  broad  foundations  of 
Bernard  and  M tiller  developed  along  two  independent 
pathways — the  physical  and  the  chemical.  We  find  a 
group  of  physiologists,  among  whom  Weber,  Ludwig, 
Du  Bois,  Reymond  and  Helmholtz  were  note- 
worthy leaders,  devoted  to  the  investigations  of 
physiological  facts  through  the  application  of  meas- 
urements and  records  made  by  mechanical  means. 
With  these  men  came  into  use  the  time-markers,  the 
kymographs,  and  other  ingenious  methods  that  have 
been  adopted  by  Zoology,  Physics  and  other  sciences. 
The  investigation  of  vital  activities  by  means  of 


GENERAL  PHYSIOLOGY  83 

graphic  records  made  by  instruments  of  precision  has 
come  to  represent  one  especial  phase  of  modern 
physiology. 

The  other  marked  line  of  physiological  investiga- 
tion has  been  in  the  domain  of  chemistry,  where 
Wohler,  Liebig,  Kiihne,  and  others  have,  through  the 
chemical  changes  occurring  in  its  body,  observed  the 
various  activities  that  take  place  within  the  or- 
ganism. Some  of  the  more  recent  observations  have 
made  a  particular  feature  of  the  study  of  chemical 
changes  taking  place  within  living  matter.  The 
prodigious  development  of  organic  and  biological 
chemistry  has  shown  the  close  interrelationship  of 
chemistry,  physiology  and  biology. 

The  physiological  method  has  been  much  applied 
in  zoological  study.  Besides  the  important  investiga- 
tions carried  on  by  zoologists  under  the  title  of 
"Experimental  Morphology"  there  has  arisen  a 
recognized  division  designated  experimental  zoology 
which  is  chiefly  physiological. 

General  physiology  is  so  intimately  related  that  all 
students  of  zoology  should  take  occasion  to  become 
acquainted  with  Verworn's  admirable  treatise  on 
General  Physiology. 


CHAPTER  IX 
THE  ANIMAL  KINGDOM 

IT  is  common  phraseology  to  speak  of  the  great 
province  embracing  all  animals  as  "The  Animal 
Kingdom."  Linnaeus  employed  the  designations 
"Animal  Kingdom,"  "Plant  Kingdom"  and  "Min- 
eral Kingdom"  to  indicate  the  three  kingdoms  of 
nature;  and  the  title  of  Cuvier's  general  zoology  was 
The  Animal  Kingdom  Arranged  According  to  its 
Organization. 

One  phase  of  zoology  has  for  its  aim  to  give  a 
descriptive  inventory  of  the  animal  kingdom.  We 
should  remember,  however,  that  this  is  merely  one 
aspect  of  zoology.  In  early  times,  it  was  the  dom- 
inate feature  of  zoological  study,  but  it  is  now  subor- 
dinate in  importance  to  those  phases  of  the  subject 
that  deal  with  structure,  development,  physiology, 
habits,  etc.  The  orderly  arrangement  of  animals  into 
natural  groups  of  different  rank  should  be  the  out- 
come of  a  study  of  their  structure  and  life  histories. 

In  the  time  of  Linnaeus,  the  classification  of 
animals  was  based  on  observations  of  the  external 
resemblances  and  differences  and,  later,  the  internal 

84 


THE  ANIMAL  KINGDOM  85 

structure  was  taken  into  account  for  the  same  pur- 
pose. At  the  present  time,  however,  and  ever  since 
the  doctrine  of  descent  began  to  be  accepted,  nat- 
uralists have  had  a  better  criterion  for  determining 
relationships.  Animals  exhibit  relationships  because 
they  have  sprung  from  a  common  stock.  The  mem- 
bers of  a  natural  group  resemble  each  other  in  struc- 
ture because  they  have  a  genetic  relationship  and 
those  that  are  closest  allied  have  a  closer  kinship. 
When  the  entire  animal  series  is  spoken  of  as  the 
Animal  Kingdom,  the  large  natural  subdivisions  of 
the  territory  formerly  were  called  subkingdoms,  but, 
at  present,  the  designation  commonly  employed  for 
each  subdivision  is  Phylum  (from  the  Greek  phylos, 
a  tribe).  There  is  no  agreement  among  zoologists  as 
to  the  number  of  phyla  into  which  the  animal  king- 
dom should  be  divided.  "  Some  authorities  recognize 
only  eight,  while  others  maintain  that  there  should 
be  as  many  as  twenty  or  even  more."  Such  extensive 
subdivision  of  even  the  primary  groups  is  probably 
justified  on  technical  grounds,  but,  as  Richard 
Hertwig  has  remarked:  "In  this  way  groups  poor  in 
species  and  of  little  importance  in  a  general  account 
of  the  animal  kingdom  are  placed  on  the  same  basis 
as  the  large  and  exceedingly  important  groups  of 


86       THE  MAIN  CURRENTS  OF  ZOOLOGY 

vertebrates,  arthropods  and  molluscs  and  thus  ob- 
tain, especially  in  the  eyes  of  the  beginner,  an 
importance  which  does  not  belong  to  them." 

For  our  present  purpose,  it  will  be  sufficient  to 
enumerate  and  briefly  characterize  the  ten  phyla 
which  embrace  nearly  all  animals  except  those  of 
somewhat  uncertain  position.  While  merely  the 
phyla  are  mentioned  here,  it  is  to  be  understood  that 
the  division  of  these  large  groups  into  classes,  orders 
and  families  brings  us  by  groups  of  different  rank  to 
genera  and  species.  The  latter  divisions  supplying 
the  generic  and  specific  name  by  which  individual 
animals  are  known. 

I.  Protozoa. — The  simplest  microscopic,  usually 
aquatic,  single-celled  animals.  In  these  animals,  the 
manifestations  of  life  are  reduced  to  their  simplest 
expression  and  a  study  of  them  is  the  best  introduc- 
tion to  the  more  complex  animals  and  also  the  best 
introduction  to  general  physiology.  Certain  forms 
are  disease-producing  or  pathogenic,  as  the  germ  of 
malaria,  of  sleeping  sickness,  etc.  Although  very 
minute,  certain  kinds  of  protozoa  commonly  occur  as 
fossils.  Those  producing  shells  of  carbonate  of  lime 
making  beds  of  chalk,  and  those  forming  shells  of 
silica  occurring  in  fossiliferous  earths.  The  known 


THE  ANIMAL  KINGDOM  87 

Protozoa  number  about  8500  living  and  200  fossil 
species. 

n.  Porifera. — The  sponges,  chiefly  marine  an- 
imals composed  of  many  cells  surrounding  pores  and 
channels  through  which  water  circulates  freely. 
Besides  budding,  they  are  reproduced  by  eggs  and 
sperms.  The  soft  living  "sponge-flesh"  is  usually 
supported  by  spicules  and,  in  different  varieties,  by 
skeletons  of  horny,  calcareous  or  silicious  material. 
The  horny  sponges  are  of  commercial  importance. 
The  calcareous  sponges  and  glass  sponges  are  fre- 
quently found  as  fossils.  Fresh  water  sponges, 
usually  inconspicuous,  are  widely  distributed  but  of 
no  commercial  value.  Approximately  2  500  living  and 
800  fossil  species  are  known. 

III.  Coelenterata. — A  group  of  slightly  complex 
animals  embracing  the  fresh  water  hydra  and  nu- 
merous salt  water  forms,  as  the  polyps,  jelly-fish, 
coral-forming  animals,  etc.  They  exhibit  a  radial 
arrangement  of  parts  and  most  of  them  possess 
peculiar  stinging  cells.  The  first  distinctly  developed 
nervous  system  and  sense-organs  appear  in  this 
group.  Four  thousand  two  hundred  living  and  nearly 
2000  fossil  species  are  recognized. 

The  animals  formerly  grouped  under  the  general 


88       THE  MAIN  CURRENTS  OF  ZOOLOGY 

heading  Vermes  present  diverse  and  often  puzzling 
relations.  It  is  now  universally  recognized  that  there 
is  no  natural  group  or  phylum  "vermes"  but  the 
title  is  often  retained  on  account  of  its  convenience. 
The  title  is  justifiable  only  as  a  popular  name  for 
shape.  The  animals  included  under  it  do  not  form  a 
natural  group  of  related  species  and  the  general 
tendency  is  to  split  the  group  into  at  least  three 
phyla, — the  flatworms,  the  roundworms  and  the 
segmented  worms  or  annelida.  The  brachiopod, 
which  are  so  abundant  as  fossils  (500x3  species)  are 
frequently  classified  as  shelled  worms;  at  other 
times,  they  are  separated  into  an  independent  phy- 
lum, or  are  united  with  the  bryozoa  into  a  phylum 
molluscoida. 

IV.  Platyhelminthes. — This  phylum  of  flatworms 
includes  fresh  water,  salt  water  and  land  planarians 
and  parsitic  forms.    The  parasitic  flatworms,  such  as 
tapeworms,   liver-flukes,   etc.,   are   responsible   for 
certain  diseases  of  man  and  other  animals.     Four 
thousand  six  hundred  species  are  known. 

V.  Nemathelminthes. — The  roundworms  or  thread- 
worms are  chiefly  small  parasitic  worms,  living  in 
the  alimentary  canal,  the  blood  or  the  tissues  of 
man  and  other  animals.    The  hookworm,  respon- 


THE  ANIMAL  KINGDOM  89 

sible  for  much  misery  and  shiftlessness  among  the 
"poor  whites"  of  the  south,  is  an  example.  Other 
common  illustrations  are:  The  harmless  "Vinegar- 
eel"; — the  pin  worm  of  the  alimentary  canal;  the 
Trichinella,  which  imbeds  itself  in  the  muscles  and 
comes  from  infected  and  imperfectly  cooked  pork; 
the  Filaria,  a  blood  parasite,  etc.  One  thousand  five 
hundred  living  species  are  recognized. 

VI.  Annelida. — The  segmented  worms  embrac- 
ing the  earthworm,  the  leeches  and  others.  Some 
forms  burrow  in  the  earth,  others  inhabit  fresh  water 
(leeches),  and  salt  water  (Nereis).  About  4000 
living  species  are  known. 

VH.  Echinodermata. — Marine  animals  with  a 
spiny  skin  or  a  calcareous  test  covering  the  soft  parts. 
The  sea  cucumbers,  the  starfishes,  sea  urchins,  sea- 
lillies,  etc.,  belong  to  this  group.  They  exhibit  a 
radial  arrangement  of  parts.  Locomotion  is  usually 
by  tube-feet  connected  with  a  characteristic  water 
vascular  system.  There  are  known  approximately 
3000  living  and  2600  fossil  forms. 

Vm.  Arthropoda. — Contains  the  largest  number 
of  species  of  any  phylum.  Separated  from  all  forms 
of  worms  by  possessing  jointed  appendages.  The 
phylum  embraces  several  large  classes  as:  (i)  Cms- 


90       THE  MAIN  CURRENTS  OF  ZOOLOGY 

tacea,  lobster,  crayfishes,  shrimps,  sow-bugs,  etc. 
(2)  Insecta,  an  enormous  group  containing  about 
400,000  described  living  and  5000  fossil  species. 
Very  interesting  for  exhibiting  serial  homology  of  the 
appendages.  These  structures,  although  all  equiva- 
lent, and  arising  in  the  same  manner,  are,  under 
certain  conditions,  transformed  into  jaws,  antennae, 
walking-limbs,  swimerets,  etc.  The  insects  exhibit 
more  clearly  than  any  other  animals  the  phenomona 
of  metamorphosis  such  as  the  development  of  a 
worm-like  larva  through  the  chrysalis  stage  into  the 
winged  insect.  These  animals  are  also  immensely 
interesting  on  account  of  their  relation  to  the  fer- 
tilization of  flowers,  their  habits,  their  communal 
life  and  as  disease  carriers.  (3)  Myriopoda}  centi- 
peds,  "thousand-legged  worms,"  etc.  (4)  Arachnida, 
or  spiders,  notable  as  web-spinners.  This  class  in- 
cludes scorpions,  Limulus  (the  king-crab)  and  others. 
IX.  Mollusca. — Slugs,  snails,  clams,  oysters, 
squids,  cuttle-fish,  devil-fish,  etc.  Although  the  name 
mollusca  is  from  the  Latin  Mollis,  meaning  soft,  this 
applies  only  to  the  bodies  of  these  animals;  a  large 
number  of  them  secrete  shells  which  circumstance 
makes  them  of  frequent  occurrence  as  fossils.  About 
60,000  living  and  21,000  fossil  forms  are  known. 


THE  ANIMAI^  KINGDOM  91 

X.  Vertebrate. — The  most  highly  developed  an- 
imals, those  above  the  simplest  ones  possessing  ver- 
tebrae, but  this  feature  is  not  common  to  all.  Ex- 
cluding Tunicates  and  Amphioxus,  five  classes  are 
recognized:  Fishes,  Amphibia,  Reptiles,  Birds  and 
Mammals.  The  latter  class  including  man.  There 
are  about  30,000  living  and  a  large  number  of  fossil 
species. 

Intermediate  between  the  molluscs  and  the 
vertebrates  are  sea-squirts,  or  Tunicates.  A  phylum 
Chordata  is  frequently  made  to  include  the  Tunicates, 
other  primitive  forms,  and  the  vertebrates  because 
all  these  animals  are  alike  in  possessing  a  notochord,  a 
dorsal  nerve-cord  and  gill-slits.  The  Tunicates  num- 
ber about  300  species. 

There  are  several  other  groups  of  invertebrates  of 
uncertain  position  but  which  are  often  elevated  into 
the  rank  of  phyla.  If  the  Brachiopods  are  classed  as 
shelled  worms,  the  most  important  of  the  remaining 
forms  are  the  Bryzoa.  These  are  moss-like,  incrusting 
animals,  inhabiting  both  salt  and  fresh  water,  and 
numbering  about  700  living  and  1800  fossil  species. 

For  a  more  detailed  analysis  of  the  animal  kingdom, 
with  sketches  and  consideration  of  the  structure  of 
types,  consult  the  various  manuals  and  text-books. 


92       THE  MAIN  CURRENTS  OF  ZOOLOGY 

The  Animal  Series. — In  a  certain  sense  animals 
constitute  a  series,  at  the  lower  end  of  which  are  the 
simple  Protozoa  and  at  the  upper  end  the  Mammals. 
However  graphic  this  conception  may  appear,  it 
needs  to  be  taken  with  proper  qualifications.  An- 
imals do  not  by  any  means  form  a  connected  series. 
There  is  much  overlapping  of  different  groups  and 
there  are  various  perplexing  offshoots — as  in  the  case 
of  the  Echinoderms.  Animals  constitute  a  series  in 
the  sense  that  they  have  a  common  ancestry  and  that 
the  higher  forms  are  derived  from  the  lower  by  a 
process  of  descent,  but  adaptations  to  different  con- 
ditions of  life  have  brought  about  many  diversities. 
The  significant  point  is  that  they  do  not  stand  as 
separate  creations  but  are  all  related  structurally, 
physiologically  and  psychologically. 

We  may  say,  the  most  striking  general  feature  of  an 
animal  is  that  it  has  not  arisen  independently,  but 
that  it  exhibits  a  genetic  similarity  with  other  mem- 
bers of  the  animal  kingdom.  The  recognition  of  the 
common  genealogy  of  animals  led  to  the  doctrine  of 
organic  evolution.  It  also  prepares  us  to  understand 
that  the  study  of  a  few  selected  types  from  the  differ- 
ent natural  groups,  with  an  analysis  of  their  struc- 
ture, their  life  histories  and  their  relations  to  sur- 


THE  ANIMAL  KINGDOM  93 

rounding  conditions,  may  serve  to  open  the  whole 
field  of  zoology.  Huxley  attempted  to  do  this  by  the 
use  of  a  single  animal  in  his  famous  Introduction  to 
the  study  of  Zoology  based  upon  the  study  of  the 
Crayfish  in  all  its  essential  relations  to  other  animals 
and  to  nature  at  large. 

The  study  of  types  is  a  good  procedure,  but  how 
to  avoid  having  this  method  lead  merely  to  accumu- 
lation of  a  certain  set  of  facts  regarding  animals  is  a 
matter  of  much  concern,  since  that  has  been  the 
result,  in  so  many  cases,  of  holding  exclusively  to  this 
plan.  As  stated  in  an  earlier  chapter,  what  is  lacking 
in  this  method  is  concurrent  attention  to  the  back- 
ground of  the  subject — information  about  the  condi- 
tions under  which  the  subject  developed,  the  cir- 
cumstances that  made  possible  its  advances,  the  men 
who  accomplished  results  and  an  orderly  though 
brief  account  of  the  steps  in  its  development. 

The  Number  of  Animals. — The  number  of  known 
animals  is  ever  increasing  by  descriptions  of  new 
species.  Aristotle  mentioned  about  500  but  probably 
knew  more.  Linnaeus,  in  1758,  described  4236 
species.  About  a  hundred  years  later,  Agassiz  and 
Brown  listed  129,530.  In  1886,  Ludwig's  revision  of 
Leunis's  Animal  Kingdom  gives  273,220,  and  Pratt, 


94       THE  MAIN  CURRENTS  OF  ZOOLOGY 

in  1911,  enumerates  522,400.  This  represents  only 
the  named  species  of  living  animals  and  is  far  short 
of  the  actual  number.  In  Pratt's  enumeration  there 
are  360,000  insects.  We  are  to  understand  that  the 
number  of  living  species  is  much  larger  since  there 
are  many  that  have  not  been  described  and  classified. 


CHAPTER  X 
ZOOLOGY  OF  FOSSIL  REMAINS 

THERE  is  one  large  division  of  zoology  not  yet 
touched  upon — the  study  of  the  remains  of  extinct 
animals.  This  is  obviously  a  department  of  zoology 
although  it  is  more  frequently  placed  with  geology 
under  the  name  of  paleontology.  The  extinct 
animals  were  ancestors  of  those  now  living  and  many 
revelations  are  found  by  studying  their  fossil  re- 
mains. The  fossil  remains  of  animals  are  so  nu- 
merous and  cover  such  a  long  range  of  tune,  that  we 
have  preserved  in  the  rocks  not  only  a  picture  of  the 
succession  of  animal  life  on  the  globe  for  many  cen- 
turies, but,  also,  records  of  the  transmutations  or  the 
structural  changes  they  have  undergone.  These  open 
such  a  wide  sweep  of  observation  that  they  are  of 
incalculable  value  in  the  study  of  zoology. 

It  is  estimated  that  if  the  fossil  bearing  rocks  were 
accumulated  in  one  series  they  would  measure  more 
than  forty  miles  in  thickness  and  represent  a  period 
of  several  millions  of  years  in  their  formation.  Exam- 
ination of  the  fossils  from  the  lower  rocks  shows  that 

for  many  aeons  there  were  no  vertebrate  animals,  and, 

95 


96       THE  MAIN  CURRENTS  OF  ZOOLOGY 

that  for  the  duration  of  many  additional  seons,  the 
only  living  vertebrates  were  Fishes.  From  the  fishes 
were  gradually  evolved  the  amphibians,  the  reptiles, 
the  birds  and,  finally,  the  mammals.  All  these 
changes  requiring  immense  stretches  of  time  took 
place  before  the  advent  of  man. 

From  tune  to  time  the  fossil  series  exhibits  interest- 
ing connecting  links  such  as  the  curious  tailed  and 
toothed  bird,  the  archaeopteryx,  showing  structural 
relations  between  reptiles  and  birds. 

The  science  of  fossil  remains  is  not  only  an  off- 
shoot of  zoology  but  as  before  stated  it  was  founded 
by  zoologists;  Cuvier  being  the  recognized  founder 
of  vertebrate  and  Lamarck  of  invertebrate  paleontol- 
ogy. This  science  was  extensively  developed  by 
Zittel,  the  paleontologist  of  Munich,  and  by  Cope 
(Fig.  20),  Leidy  (Fig.  21),  and  Marsh  in  the  United 
States  as  well  as  by  more  recent  workers. 

Extensive  progress  has  been  made  within  the  past 
twenty-five  years  in  observations  of  the  fossil  animals 
and  among  other  advances  the  genealogy  of  several 
living  families  of  mammals  has  been  traced.  Notable 
studies  have  been  made  on  the  ancestry  of  Camels, 
Elephants,  etc.  The  most  thoroughly  known  an- 
cestral history  is  that  of  the  horse.  The  zoological 


F'G.  20. — E.  D.  COPE  (1840-1897)  FIG.  21. — JOSEPH  LEIDY  (1823-1891) 


FIG.  22. — CHARLES  SEDGWICK  MINOT         FIG.  23. — CHARLES  OTIS  WHITMAN 

(1852-1914)  (1842-1910) 


ZOOLOGY  OF  FOSSIL  REMAINS  97 

history  of  this  animal  is  a  hackneyed  theme  but, 
nevertheless,  very  convenient  for  reference.  Al- 
though not  old  hi  comparison  with  the  earlier  animal 
life,  a  quite  close  series  of  fossil  remains  shows  the 
development  of  the  horse  family  through  a  period  of 
3,000,000  years.  The  earliest  authenticated  ancestor 
of  this  race  began  in  the  Eocene  period  with  an  animal 
having  a  four-toed  limb  in  front  and  a  five-toed  one 
behind.  About  the  size  of  a  fox,  this  eohippus  was 
the  ancestor  of  the  horse  tribe.  From  this  point,  the 
descendants  of  the  original  forms  show  the  structural 
modifications  through  which  the  family  of  horses 
passed,  until  we  arrive  at  the  recent  horse  with  a 
single  toe  on  both  fore  and  hind  feet,  with  the  molar 
teeth  modified  and  fitted  for  its  food  of  grass  and 
grain. 

In  the  museum  at  Yale  University  and,  notably, 
in  the  American  Museum  of  Natural  History  in  New 
York  City,  are  preserved  a  large  number  of  the  fossil 
remains  of  these  animals.  The  development  was  not 
that  of  a  single  kind  of  horse  but  parallel  development 
of  several  varieties  some  of  which  have  become 
extinct  and  others  continued.  It  is  a  difficult 
problem  to  keep  separate  the  straight  line  of  ancestry 
of  our  modern  horse,  but  the  material  now  accu- 


98       THE  MAIN  CURRENTS  OF  ZOOLOGY 

mulated  enabled  Professor  Henry  F.  Osborn,  and 
others,  to  separate  the  equus  line  from  the  other  fossil 
horses  and  to  indicate  the  direct  line  of  descent. 

From  the  zoological  standpoint  especial  interest 
has  centered  about  the  fossil  remains  of  man  and  of 
pre-humans  that  are  throwing  light  on  the  question 
of  human  lineage. 

The  story  of  prehistoric  man  is  imperfectly  known, 
although  sporadic  explorations  have  already  accu- 
mulated an  interesting  series  of  evidences  bearing  on 
the  subject,  such  as  primitive  stone  implements  of 
human  manufacture,  crude  sketches  of  extinct 
animals  by  prehistoric  artists,  and  fossil  remains  of 
primeval  man  showing  gradations  in  the  shape  and 
the  capacity  of  skulls.  All  these  correlated  sources 
afford  most  convincing  proofs  of  man's  great  antiq- 
uity. He  has  left  traces  of  his  occupancy  of  the 
earth,  especially  in  central  and  southwestern  Europe 
and  in  England,  long  before  the  dawn  of  the  historical 
period. 

The  prehistoric  stone  implements  are  found  asso- 
ciated with  the  bones  of  extinct  animals  in  caves,  and 
imbedded  in  the  strata  of  soil  and  gravel  that  have 
remained  undisturbed  for  many  centuries.  The  stone 
implements  are  of  three  grades:  Neoliths,  the  more 


ZOOLOGY  OF  FOSSIL  REMAINS  99 

recent  ones,  carefully  shaped  with  skill  and  artistic 
feeling;  Palaeoliths,  very  ancient,  rude,  but  evidently 
shaped  by  design;  and  Eoliths,  rough  stone  chips 
bearing  evidence  of  use  and  indicating  the  existence 
of  man  of  less  developed  skill.  These  latter  imple- 
ments carry  the  trace  of  a  tool-making  creature  back 
into  the  Tertiary  period. 

Besides  the  stone  implements  there  are  many 
sketches  of  extinct  animals  by  prehistoric  artists, 
scratched  on  bone,  ivory,  horn,  slate  and  on  the  walls 
of  caves.  The  inference  to  be  drawn  from  these 
sketches  is  that  man  was  alive  in  Central  and  South- 
western Europe  when  the  hairy  mammoth  and  the 
reindeer  occupied  the  same  territory.  The  crude 
sketches  of  palaeolithic  man,  just  referred  to,  merge 
by  gradations  into  the  more  carefully  drawn,  and 
sometimes  colored  sketches,  of  Neolithic  man.  Those 
of  the  cave  of  Altimera,  in  Spain,  are  very  notable 
products  of  Neolithic  artists. 

The  range  of  discovery  of  fossil  human  relics  gives 
evidence  of  a  wide  geographical  distribution  of 
primitive  races  during  palaeolithic  times.  Variations 
in  the  degree  of  skill  in  the  manufacture  of  stone 
implements,  as  well  as  in  other  particulars,  have 
brought  to  archaeologists  the  recognition  of  different 


ioo     THE  MAIN  CURRENTS  OF  ZOOLOGY 

culture  periods,  which  are  well  exhibited  in  different 
parts  of  France  and  Central  Europe.  No  less  than 
six  culture-periods  of  palaeolithic  man  are  known, 
indicating  that  the  prehistoric  period  of  human 
development  was  far  longer  than  the  entire  historic 
period. 

It  is,  however,  to  fossil  remains  of  primitive  man 
that  we  must  look  for  evidences  of  structural  changes 
that  have  taken  place  in  the  human  frame. 

Of  all  the  bony  parts,  the  skull  is  the  most  interest- 
ing for  comparison,  since  its  size  and  configuration 
indicate  in  a  general  way  the  degree  of  development 
of  the  brain,  and,  as  a  consequence,  the  relative 
grade  of  intelligence. 

One  of  the  most  famous  documents  of  man's  an- 
cestral history  is  the  well-known  Neanderthal  skull, 
discovered  in  a  cave  near  Diisseldorf  in  the  valley  of 
the  Neander,  in  1856  and  first  described  in  1857.  It 
is  now  exhibited  with  other  parts  of  the  skeleton  in 
the  provincial  museum  at  Bonn  on  the  Rhine.  The 
inferences  drawn  from  this  very  ancient  skull,  with 
its  low  receding  forehead,  showing  small  develop- 
ment in  the  region  of  the  higher  mental  faculties, 
created  a  sensation,  and  great  opposition  was  devel- 
oped in  allowing  the  discovery  to  rank  as  an  evidence 


ZOOLOGY  OF  FOSSIL  :REA3AIN}}  <-.]      >oi 

of  primitive  man.  But  its  importance  has  been 
enhanced  by  the  discovery  of  a  long  series  of  similar 
skulls. 

In  1886,  came  the  discovery  in  the  Cave  of  Spy, 
Belgium,  of  two  skeletons  with  the  same  structural 
features  as  those  of  the  Neanderthal  remains,  and, 
since  that  time,  the  discoveries  of  numerous  similar 
relics  have  established  the  existence  of  a  Neander- 
thal race  living  in  the  middle  of  the  palaeolithic 
period.  The  more  notable  members  of  the  Neander- 
thaloid  series  embrace:  the  human  remains  of 
Krapina,  in  Croatia,  found  in  1899-1904,  and  con- 
sisting of  parts  of  the  skeletons  of  ten  persons  from 
infancy  to  old  age;  the  skeletal  remains  of  La  Chapelle 
aux-saints  and  of  Le  Moustier. 

In  August,  1908,  there  was  discovered  in  South- 
western France,  by  well  directed  efforts  of  French 
archaeologists,  a  very  interesting  skeleton  of  the 
Neanderthal  type,  and  now  known  as  the  man  of  La 
Chapelle  aux-saints.  This  is  the  skeleton  of  an  old 
man  with  an  almost  complete  skull,  and  a  lower  jaw 
lacking  some  of  the  teeth.  Since  the  comprehensive 
analysis  of  these  remains,  published  by  Boule  in  1913, 
this  is  the  most  thoroughly  known  skeleton  of  the 
Neanderthal  race  and  may  be  taken  as  a  type.  Be- 


102      THE  MAJN  CURRENTS  OF  ZOOLOGY 

sides  the  structural  features  of  the  bony  parts,  it  is 
interesting  to  note  that  the  casts  of  the  interior  of 
the  cranium  show  the  surface  features  of  the  brain. 
As  compared  with  the  brain  of  modern  man,  it  is 
small  in  the  region  of  the  frontal  lobes  and  shows  a 
greater  simplicity  in  the  pattern  of  the  convolutions. 

A  somewhat  more  primitive  type  was  discovered  a 
few  months  earlier  (March,  1908)  at  the  famous 
station  of  Le  Moustier.  It  is  the  skull  of  a  young 
person  and  valuable  for  comparison. 

These  aboriginal  people  represent  one  link  of  the 
chain  of  human  ancestry,  and  they  were  followed  by  a 
higher  developed  type  of  primitive  man  before  the 
dawn  of  history  and  the  emergence  of  the  modern 
type. 

A  much  more  interesting  circumstance  is  that 
the  Neanderthal  people  were  preceded  by  more 
primitive  pre-humans.  There  are  known  at  present 
three  examples  of  remains  that  are  distinctly  pre- 
Neanderthaloid.  The  first  to  be  discovered,  and  also 
the  most  primitive  pre-human  species  known,  is 
represented  by  portions  of  the  skull,  and  of  the  leg 
bones,  found  in  Central  Java  by  the  Dutch  surgeon, 
Dubois,  during  the  years  1891  and  1892,  and  made 
known  in  1894.  These  remains  were  found  in  Ter- 


ZOOLOGY  OF  FOSSIL  REMAINS  103 

tiary  deposits  and  were  christened  with  the  name  of 
Pithecanthropus  Erectus.  The  capacity  of  the  skull, 
930  cubic  centimeters,  precludes  the  conclusion  that 
it  belongs  to  the  series  of  anthropoid  apes — the 
largest  cranial  capacity  of  apes,  living  or  fossil,  not 
exceeding  600  cubic  centimeters. 

The  second  pre-Neanderthaloid  is  the  perfect 
lower  jaw  with  all  the  teeth,  discovered  in  1907  in 
the  sands  of  Mauer,  near  Heidelberg.  These  de- 
posits belong  to  the  lower  Quarternary,  and  since  the 
discovery  of  the  Heidelberg  jaw  it  is  claimed  that 
Eoliths  have  been  discovered  in  the  same  layer. 
The  jaw,  while  distinctly  human  as  to  characteristics 
of  the  teeth,  is  very  primitive.  The  creature  to 
which  it  belongs  has  been  designated  Homo  Heidel- 
bergensis. 

The  most  recent  discovery  of  pre-human  remains 
comes  from  England.  At  Piltdown  Common,  in 
Sussex,  in  1912,  there  was  unearthed  a  skull,  with 
parts  of  the  lower  jaw  and  teeth,  that  fits  into  the 
series  of  the  pre-Neanderthaloids.  It  has  been  sug- 
gestively named  the  dawn  man  (Eoanthropus  Daw- 
sonii). 

Above  the  Neanderthal  race  come  the  numerous 
fossil  remains  of  Neolithic  man,  merging  by  struc- 


104     THE  MAIN  CURRENTS  OF  ZOOLOGY 

tural  gradations  into  those  of  recent  type.  The 
skeleton  of  Mentonne,  that  of  Combe  Chapelle  (1909), 
of  Galley  Hill  (1895),  the  Cro-magnon  race  and  other 
representatives  are  forms  that  connect  palaeolithic 
with  recent  man. 

Putting  these  discoveries  together  we  have  an 
interesting  series  of  gradations  of  skulls,  leading  one 
into  the  other,  and  covering  a  range  of  cranial  capac- 
ity from  930  cu.  cm.,  that  of  the  Java  man,  to  1480- 
1555  cu.  cm.  that  of  the  average  white  European. 
The  Neanderthal  skulls  occupy  an  intermediate 
position  with  a  cranial  capacity  of  approximately 
1400  cu.  cm. 

In  tracing  backwards  from  recent  man,  it  is  not  to 
be  assumed  that  the  ancestral  line  breaks  off  ab- 
ruptly. Even  the  Java  man  had  antecedents,  and 
it  is  natural  to  assume  his  derivation  from  an  extinct 
Primate  of  the  Earlier  Tertiary  deposits.  Positive 
evidences  are  lacking,  but  the  known  presence  of 
anthropomorphous  Primates  in  the  Miocene  of 
France  offers  a  possible  suggestion.  Paleontological 
discoveries  have  supplied  the  line  of  genealogy  of 
several  families  of  mammals,  and  if,  on  this  basis,  we 
assume  that  man  and  the  anthropoid  apes  had  a 
generalized  ancestor,  it  is  nevertheless  clear  that  the 


ZOOLOGY  OF  FOSSIL  REMAINS  105 

human  and  the  simian  lines  have  had  an  independent 
development  for  many  centuries.  There  has  been 
no  crossing  of  the  lines  since  Tertiary  times. 

The  derivation  of  man  from  an  extinct  Tertiary 
Primate  seems  already  to  be  well  authenticated. 
Furthermore,  the  fossil  records  give  evidence  of  the 
conditions  under  which  the  development  of  the 
higher  races  of  animals  began.  By  making  plastic 
casts  of  the  interior  of  the  fossil  skulls  of  Tertiary 
mammals,  it  has  been  determined  that  there  was  in 
that  geological  period  a  marked  increase  in  the  size  of 
the  brain.  This  circumstance  was  of  the  greatest 
importance  both  for  progress  and  for  perpetuity  of 
certain  kinds  of  animals.  Those,  in  particular,  whose 
increased  intelligence  enabled  them  to  cope  more 
successfully  with  the  conditions  'of  their  existence, 
and  to  turn  natural  forces  to  their  advantage,  were 
continued  and  unproved.  In  pre-humans  the  increase 
in  brain  surface  led  to  the  power  of  storing  up  im- 
pressions, and,  finally,  brought  about  a  condition  of 
educability  which  formed  the  starting  point  for 
marked  improvement.1 

1  The  above  14  paragraphs  quoted  from  the  writer's  Biology  and  Its 

Makers. 


CHAPTER  XI 

MAIN  PATHWAYS  AND  RECENT  TENDENCIES 
OF  ZOOLOGY 

AT  this  point  it  will  be  convenient  to  indicate  the 
chief  pathways  by  which  the  territory  of  zoological 
study  has  been  entered  and  explored.  Broadly 
speaking,  the  main  highways  of  zoology  are  embraced 
under  the  following  designations:  Structural  Zoology 
(Morphology),  with  its  subdivisions — comparative 
anatomy,  histology,  embryology,  and  the  study  of 
fossil  animals;  Systematic  Zoology  (Natural  History), 
comprising  classification,  ecology  (the  relation  be- 
tween animals  and  their  surroundings),  study  of 
habits  and  geographical  distribution  of  animals; 
General  Physiology  of  animals,  with  animal  psychol- 
ogy and  animal  behavior;  Experimental  Zoology, 
(which  is  more  a  method  of  general  application  than 
a  subdivision),  embracing  Genetics,  experimental 
morphology  and  similar  branches;  and,  Philosophical 
Zoology,  with  organic  evolution  and  related  topics. 
In  addition  there  are  some  miscellaneous  divisions  of 
smaller  importance. 

To  bring  these  various  subdivisions  under  bird's- 

106 


MAIN  PATHWAYS  AND  TENDENCIES     107 

eye  view  with  brief  comments  will  help  mark  the 
pathways  of  the  territory. 

Structural  Zoology. — The  two  broad  aspects  in  the 
investigation  of  animal  forms  are  morphological  and 
physiological.  Supplemental  to  one  another,  they 
embrace  the  statics  and  the  dynamics  of  animals— 
the  architecture  and  the  function.  Structural 
zoology  (or  morphology)  is  fundamental  in  providing 
a  basis  for  physiological  investigations.  It  includes 
topics  dealing  with  gross  and  minute  anatomy,  with 
the  process  of  building,  or  development  of  the  body, 
and  the  study  of  fossil  animals.  Accordingly,  we 
recognize  its  chief  subdivisions  as  comparative 
anatomy,  histology,  embryology  and  paleontology 
(paleozoology). 

Comparative  Anatomy. — The  study,  broadly  com- 
parative, of  the  structure  of  animals,  well  adapted  for 
the  early  stages  of  laboratory  observation,  usually 
pursued  by  an  examination  of  types  of  animal  life 
from  the  lowest  to  the  highest.  The  microscope  is 
necessary  for  the  examination  of  the  whole  group  of 
protozoa  and  for  other  minute  animals  such  as 
rotifers,  microscopic  Crustacea,  etc. 

Comparative  anatomy  is  chiefly  the  structural 
study  of  animals  as  to  their  organs  and  systems  of 


io8      THE  MAIN  CURRENTS  OF  ZOOLOGY 

organs,  as  the  digestive  system,  the  circulatory  sys- 
tem, the  nervous  system,  etc.  It  aims  to  establish 
homologies  between  organs  by  tracing  the  origin  and 
modifications  of  structures  occurring  in  series  of 
animals. 

Histology. — By  the  microscopic  study  of  the 
tissues  composing  the  organs  we  come  to  histology. 
This  reaches  a  deeper  level  of  morphological  analysis 
than  comparative  anatomy.  In  its  full  scope,  it  dis- 
tinguishes the  cells  as  well  as  the  tissues,  and  cytology 
is  an  offshoot  of  histology.  The  study  of  cells,  how- 
ever, has  assumed  such  importance  and  opened  so 
many  new  questions  that  cytology  stands  out  as 
an  independent  division.  The  arrangement,  the  form 
and  staining  qualities  of  cells  often  do  much  to  show 
the  use  of  tissues,  and,  therefore,  cytology  has  its 
physiological  side. 

Embryology. — This  likewise  has  become  a  broad 
subject  including  observation  of  all  stages  of  devel- 
opment from  the  egg  to  hatching — or  birth.  Among 
its  especial  topics  come  the  analysis  of  the  germinal 
elements,  the  nature  of  fertilization,  the  formation  of 
the  germ-layers,  the  physical  basis  of  heredity,  the 
histological  differentiation  (histogenesis)  of  tissues, 
etc. 


MAIN  PATHWAYS  AND  TENDENCIES     109 

Paleontology. — The  study  of  fossil  animals  (paleo- 
zoology)  is  a  division  of  morphology  since  the  in- 
vestigation of  the  physiology  of  fossil  remains  is  not 
practicable.  That  part  of  it  that  deals  with  animal 
forms  is  zoological  rather  than  geological.  It  is  a 
study  of  the  succession  of  animal  life  on  the  globe. 
In  passing,  it  should  be  remarked  that  the  succes5ion 
of  plant  life  (paleobotany)  has  been  in  recent  years 
the  field  of  very  notable  advances. 

Systematic  Zoology. — Deriving  its  name  from  the 
systematic  arrangement  of  animals  as  first  accom- 
plished in  the  Systema  Naturae  of  Linnaeus.  Since 
classification  is  based  largely  on  structural  features,  it 
would  appear  that  in  its  recent  scientific  aspects,  it 
should  be  the  outcome  of  morphological  study — and 
such  is  the  case.  But  this  was  not  so  in  earlier 
times — Systematic  Zoology  had  large  development 
before  morphology  pushed  into  prominence.  It 
arose  out  of  the  old  natural  history  of  Linnaeus.  The 
designation  natural  history  is,  however,  more  com- 
prehensive than  classification.  It  represents  the 
kind  of  study  of  animals  to  which  the  name  zoology 
was  applied  after  the  Renaissance.  After  the  rise  of 
morphology,  natural  history  continued  to  develop 
and  took  on  modern  form.  To  this  division  belongs 


i  io     THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  classification  of  animals  for  which  the  modern 
name  is  taxonomy.  From  it  arose  the  study  of  field 
zoology,  with  such  offshoots  as  ecology,  the  study  of 
habits,  and,  of  the  geographical  distribution  of 
animals. 

Work  in  ecology — the  study  of  the  relations  be- 
tween animals  and  their  surroundings — has  been 
very  active  in  the  last  decade.  There  has  been 
developed  an  extensive  technique  for  experimental 
observation  of  animals,  special  societies  have  arisen, 
text-books  and  periodicals  for  the  publication  of 
results  of  ecological  study  have  been  started.  Geo- 
graphical distribution  of  animals  is  also  allied  to 
natural  history. 

General  Physiology. — The  most  significant  thing 
about  an  animal  is  that  it  is  endowed  with  life  and 
the  analysis  of  those  vital  processes  that  are  an  ex- 
pression of  its  life,  should  go  hand  in  hand  with  the 
study  of  its  structure.  Zoology  that  is  limited  to 
study  of  the  architecture  of  animals  manifestly  is  in- 
adequate. General  physiology  of  organisms  is  as  much 
a  part  of  zoology  as  is  morphology  but  it  is  not  so 
frequently  utilized  in  courses  of  study.  The  subject 
as  related  to  zoology  embraces  a  general  considera- 
tion of  the  principles  upon  which  all  physiological 


MAIN  PATHWAYS  AND  TENDENCIES     in 

operations  depend — responses  to  stimuli,  fermenta- 
tion and  digestion,  circulation,  secretion,  excretion, 
reproduction  of  animals,  etc.  But  physiology  is  also 
an  independent  science,  pursued  for  its  own  sake,  and 
statements  like  those  just  made  are  not  to  be  taken 
even  to  imply  that  physiology  in  this  sense  is  a  part 
of  zoology.  A  parallel  situation  exists  in  reference  to 
anatomy,  which  is  a  separate  science,  whilst  the 
comparative  anatomy  of  animals  is  a  major  subject 
of  zoology.  Physiology,  is  broadly  biological,  and 
this  constant  overlapping  of  closely  related  subjects  is 
to  be  expected. 

The  study  of  the  reactions  of  the  protozoa  to  va- 
rious stimuli  has  been  much  cultivated — both  in 
zoology  and  in  physiology — since  these  organisms 
exhibit  life  in  relatively  simple  expressions.  The 
illuminating  quality  of  such  experimental  studies  has 
been  so  fully  recognized,  that  modern  text-books  on 
human  physiology,  in  most  cases,  begin  with  an 
analysis  of  the  properties  of  protoplasm  and  the 
physiological  reactions  of  the  protozoa.  This  is  the 
best  means  of  introduction  to  the  study  of  experi- 
mental physiology. 

Animal  Psychology  and  Animal  Behavior. — The 
divisions  of  animal  psychology  and  animal  behavior 


ii2     THE  MAIN  CURRENTS  OF  ZOOLOGY 

may  be  considered  as  offshoots  of  general  physiology. 
In  recent  years,  these  subjects  have  become  much 
cultivated  fields  by  zoologists  and  psychologists. 
The  results  of  these  studies  throw  light  on  some  of 
the  basal  problems  of  the  development  of  animal 
intelligence  and  afford  means  of  estimating  the  men- 
tal equipment  of  different  animals.  A  few  suggestive 
titles,  taken  at  random,  supply  illustrations — The 
Mental  Powers  of  Spiders,  by  the  Peckhams,  a  widely- 
known  study  in  comparative  psychology;  The  Be- 
havior of  Lower  Organisms,  by  H.  S.  Jennings;  Ro- 
mane's  Starfish,  Sea-urchins  and  Echinoderms,  a 
study  of  physiological  response;  Chapters  on  the 
reactions  of  the  Protozoa  in  the  classical  General 
Physiology  of  Max  Verworn. 

The  mental  evolution  of  animals  is  extremely 
interesting  as  affording  illustrations,  on  another  side, 
of  that  oneness  of  nature,  the  recognition  of  which  as 
we  have  seen  is  one  of  the  results  of  zoological  study. 
Just  as  there  are  gradations  of  structure  connecting 
the  lower  and  the  higher  animals  (the  specialized 
arising  by  modifications  from  simpler  ones)  so,  in  the 
rise  of  animal  intelligence,  there  is  a  graded  series  of 
states  keeping  pace  with  the  structural  differentiation 
of  the  nervous  system. 


MAIN  PATHWAYS  AND  TENDENCIES     113 

Investigations  in  these  fields  have  become  so 
numerous  that  special  periodicals  have  been  estab- 
lished for  the  publication  of  researches  of  animal 
psychology  and  of  animal  behavior. 

Experimental  Zoology. — This  is  rather  a  method 
of  broad  application  than  a  subdivision  of  zoology, 
and  bearing  this  in  mind,  it  forms  a  convenient  cap- 
tion under  which  to  introduce  several  topics  as  Gen- 
etics, Mendelian  Inheritance,  Experimental  Morph- 
ology, Experimental  Embryology  and  Experimental 
Cytology. 

Genetics. — Genetics,  or  the  science  of  inheritance, 
has  been  the  scene  of  great  activity,  has  developed 
until  it  stands  as  a  much  pursued  independent  divi- 
sion of  zoology.  Experiments  on  the  breeding  of 
plants  (corn,  wheat,  flowers,  etc.)  and  animals  have 
brought  great  extensions  of  knowledge  regarding  the 
growth  and  the  conditions  of  inheritance  in  or- 
ganisms. 

Mendelism. — The  whole  subject  of  heredity  has 
been  pursued  by  experimental  methods  giving  rise 
to  a  large  number  of  special  researches  too  numerous 
even  to  summarize.  One  feature  that  has  occupied 
the  center  of  the  field  is  the  study  of  Mendelian 
inheritance.  This  is  properly  a  subdivision  of 


ii4     THE  MAIN  CURRENTS  OF  ZOOLOGY 

Genetics,  but  owing  to  the  great  prominence  of  the 
subject  it  is  treated  separately.  Referring  to  Chap- 
ter IV  for  a  statement  of  Mendel's  law  of  alternative 
inheritance,  we  can  say  that  it  has  been  demon- 
strated in  poultry,  guinea  pigs,  rabbits  and  other 
animals.  The  fruit-fly  which  breeds  rapidly  and  is 
easily  kept  under  observation,  has  proved  an  ex- 
cellent subject  for  observations  of  the  effects  of 
crossing  and  the  study  of  unit  characters.  Morgan 
and  his  students  have  made  extensive  contributions 
to  the  study  of  heredity  with  this  insect.  They  have 
added  much  to  support  the  conclusion  that  the 
chromosomes  are  the  normal  mechanism  for  the 
transmission  of  Mendelian  characteristics. 

Experimental  Morphology. — The  earlier  experi- 
ments of  the  last  part  of  the  nineteenth  century  were 
carried  on  under  the  name  of  experimental  mor- 
phology— experiments  on  animals  with  a  view  to 
determine  the  changes  undergone  by  changed  condi- 
tions of  life.  Placing  eggs  and  developing  organisms 
under  different  conditions  of  environment  and  ob- 
serving the  results.  The  eggs  and  larvae  of  aquatic 
forms  are  especially  adapted  for  experiments  of  this 
nature — inasmuch  as  the  chemical  and  thermal  en- 
vironment can  be  easily  changed.  The  entire  sur- 


MAIN  PATHWAYS  AND  TENDENCIES     115 

roundings  can  be  materially  changed  by  dissolving 
chemical  salts  not  injurious  to  life  in  the  water 
inhabited  by  these  organisms.  Observations  with 
this  kind  of  experimentation  have  been  very  helpful 
in  attacking  problems  of  the  life  of  organisms. 

Experiments  on  regeneration  and  conditions  of 
growth  have  been  numerous,  and  experiments  on 
fertilization,  both  with  sperms  and  with  chemical 
salts,  are  among  those  which  have  yielded  important 
results.  In  this  connection  should  be  mentioned  the 
experiments  of  Loeb  on  artificial  parthenogenesis  and 
of  Lillie  on  the  nature  of  the  fertilization  process. 

Wilhelm  Roux,  who  has  done  very  notable  work  in 
experimental  morphology,  has  established  a  special 
periodical  (Archiv  fur  Entwickelungs  Mechanik)  for 
the  researches  in  this  field. 

Philosophical  Zoology. — The  profound  changes  in 
thought  produced  by  the  establishment  of  the  doc- 
trine of  organic  evolution,  and  its  effects  upon  our 
interpretations  of  nature,  gave  rise  to  the  division 
of  philosophical  zoology.  In  this  field  are  included 
the  rise  of  evolutionary  thought  and  the  formula- 
tion of  the  different  theories  of  organic  evolution. 
The  latter  are  attempts  to  designate  the  physical 
agency  or  agencies  that  have  operated  to  bring  about 


n6     THE  MAIN  CURRENTS  OF  ZOOLOGY 

organic  evolution,  the  truth  of  which  is  so  clearly 
evidenced  by  the  facts  of  comparative  anatomy,  of 
embryology  and  of  paleontology.  Philosophical 
interpretations  of  development,  of  heredity,  and  of 
other  zoological  generalizations,  also  come  under  this 
division  of  zoology. 

Miscellaneous  Divisions. — Zoology  has  been 
broadened  and  enriched  by  the  cultivation  of  especial 
lines  of  interest  and  this  has  led  to  an  arbitrary  sub- 
division of  some  of  the  larger  provinces.  The  position 
of  some  of  these  subjects  is  not  clearly  defined  and 
they  owe  their  prominence  to  particular  interest  in 
their  applications.  Others  of  the  miscellaneous  group 
are  clearly  offshoots  from  the  larger  divisions. 

Eugenics. — The  subject  of  Eugenics  (a  subdivision 
of  Genetics)  commands  at  present  a  large  place. 
This  scientific  study  of  the  conditions  that  may  im- 
prove or  impair  the  racial  qualities  is  properly  under- 
taken only  on  a  broad  knowledge  of  biology  and, 
especially,  of  zoology.  As  previously  stated  it  was 
especially  fostered  by  Francis  Galton. 

Protozoology. — In  reference  to  unicellular  organ- 
isms, a  department  of  protozoology  has  been  created 
with  especial  reference  to  pathogenic  protozoa.  But, 
quite  outside  the  question  of  disease-producing 


MAIN  PATHWAYS  AND  TENDENCIES     117 

protozoa,  it  has  long  been  recognized  that  in  order  to 
understand  the  real  nature  of  living  organisms  one 
must  first  become  acquainted  with  the  phenomena  of 
the  Protozoa.  The  study  of  this  single  group  has 
assumed  so  much  prominence  that,  already  there  has 
been  established  in  several  universities  a  professor- 
ship of  Protozoology. 

The  study  of  the  lif  e  history  of  pathogenic  protozoa, 
of  parasitic  worms  and  of  other  disease-producing 
and  disease-carrying  animal  organisms  has  devel- 
oped into  a  department  of  Parasitology. 

The  application  of  zoological  facts  to  the  benefit  of 
mankind  is  a  considerable  feature  of  present-day 
work.  This  is  a  continuation  and  extension  of  the 
work  inaugurated  by  Pasteur.  Under  this  general 
head  are  included  the  demonstration  of  the  connec- 
tion between  insects  and  the  propagation  of  yellow 
fever,  malaria,  sleeping-sickness,  typhoid  fever  and 
other  disorders.  Although  still  in  their  infancy 
much  benefit  has  already  accrued  from  zoological 
studies  of  this  character. 

Economic  Entomology. — Investigations  in  economic 
entomology  have  become  very  active.  They  have 
been  stimulated  by  the  economic  need  of  the  control 
of  the  ravages  by  insect  pests  that  have  attacked 


n8     THE  MAIN  CURRENTS  OF  ZOOLOGY 

crops,  fruit  and  shade  trees.  In  response  to  this 
practical  need,  the  researches  on  structure,  habits, 
life  history,  development,  conditions  of  life,  etc.,  of 
insects  have  been  greatly  increased.  A  host  of 
specially  trained  observers,  widely  distributed  over 
the  country,  have  produced  important  economic  re- 
sults which  at  the  same  time  have  greatly  advanced 
zoological  knowledge.  The  Bureau  of  Entomology 
at  Washington  has  been  the  center  promoting  this 
kind  of  investigation  and  the  results  have  been 
characterized  by  accuracy  and  scientific  production 
of  a  high  order.  Some  states  and  cities  have  well- 
organized  departments  for  carrying  on  observations 
of  this  nature. 

Marine  Zoology. — The  investigation  of  marine  life 
has  been  greatly  developed  by  exploring  expeditions 
and  by  the  establishment  of  seaside  stations.  The 
most  famous  of  these  is  the  international  research 
station  at  Naples  (Stazione  Zoologicd)  founded  by 
Anton  Dohrn  in  1872.  Tables  and  rooms  for  re- 
search in  this  station  are  maintained  partly  by  the 
cooperation  of  universities  and  learned  societies  of 
the  world.  Researches  carried  on  at  the  station  are 
by  no  means  confined  to  marine  zoology,  but  the 
marine  forms  that  are  so  abundant  in  the  gulf  of 


FIG.  24. — Louis  AGASSIZ  (1807-1873) 


MAIN  PATHWAYS  AND  TENDENCIES     119 

Naples  are  used  for  the  investigation  of  the  widest 
range  of  zoological  problems. 

In  the  United  States,  Louis  Agassiz  (Fig.  24)  was 
the  pioneer  with  his  marine  station  started  in  1873 
on  the  island  of  Penikese,  Massachusetts.  The 
Marine  Biological  station  at  Woods  Hole,  Mass- 
achusetts, is,  in  a  sense,  the  successor  of  the  Penikese 
laboratory.  It  was  chiefly  developed  by  Whitman 
(1842-1910)  who  had  been  a  student  under  Agassiz. 
The  influence  of  Whitman  (Fig.  23)  on  the  develop- 
ment of  American  zoology  was  very  great.  Besides 
acting  as  Director  of  the  station  at  Woods  Hole  for 
nineteen  years,  he  was  a  professor  at  Clark  Univer- 
sity and  afterwards  of  the  University  of  Chicago. 
He  founded  the  Journal  of  Morphology  and  carried  it 
through  seventeen  volumes.  The  greatness  of  Whit- 
man was  in  his  large  noble  spirit,  his  philosophical 
cast  of  mind  and  the  feeling  of  uplift  which  he  im- 
parted to  his  students  and  to  other  zoologists. 

Other  marine  stations  of  the  United  States  on  the 
Atlantic  Coast  as  Cold  Spring  Harbor,  New  York, 
South  Harpswell,  Maine,  Dry  Tortugas,  Florida,  and 
Beaufort,  North  Carolina,  are  supplemented  by 
those  of  the  Pacific  Coast  as  the  Puget  Sound  Station 
at  Friday  Harbor,  Washington,  Ocean  Grove,  Cal- 


120     THE  MAIN  CURRENTS  OF  ZOOLOGY 

ifornia,  La  Jolla,  California,  and  other  places.  In 
Great  Britain  the  leading  station  is  at  Plymouth, 
while  the  marine  stations  of  other  European  coun- 
tries are  numerous  and  important. 

The  explorations  of  the  abysmal  depths  and  the 
survey  of  the  sea  bottom  have  resulted  in  extension  of 
zoological  knowledge.  These  explorations  of  this 
character  have  been  carried  on  by  various  govern- 
ment expeditions.  The  notable  voyage  of  the  Chal- 
lenger (1872-1876),  has  led  to  the  publication  of 
monumental  reports  written  by  the  cooperation  of 
zoologists  of  the  different  parts  of  the  world.  The 
recent  Siboga  expedition  of  Holland  and  the  Harri- 
man  expedition  of  the  United  States  brought  much 
additional  information  about  sea  animals.  To  this 
class  of  voyages  belong  those  on  which  Darwin  (The 
Beagle)  and  Huxley  (The  Rattlesnake)  made  their 
trips  as  naturalists. 

A  department  of  oceanography  has  been  created 
as  a  division,  chiefly  of  zoology,  and  in  deep  sea 
investigations  Sir  John  Murray  of  England  and 
Alexander  Agassiz  of  the  United  States  made  notable 
observations.  Albert  L,  Prince  of  Monaco,  main- 
tains a  station  of  oceanography  on  the  French  coast. 
This  station  is  splendidly  equipped,  and  important 


MAIN  PATHWAYS  AND  TENDENCIES     121 

contributions  to  knowledge  have  resulted  from  the 
investigations  which  are  published  in  periodicals  of 
the  station. 

Limnology. — Fresh  water  stations  have  been  estab- 
lished at  many  points  in  the  United  States  and  in 
other  countries  in  which  the  fauna  of  lakes  and  rivers 
have  been  scientifically  studied.  The  pioneer  station 
of  this  class  was  established  by  Zacharias  at  Plon, 
Holstein.  Investigation  of  the  biology  of  lakes  and 
rivers  is  designated  Limnology  and  work  of  this 
nature  has  assumed  considerable  importance. 

In  connection  with  aquatic  observations,  there  has 
developed  the  plankton  work,  consisting  of  studies, 
both  qualitative  and  quantitative,  of  the  minute 
floating  life  of  waters. 

Certain  Recent  Tendencies. — The  development 
of  the  experimental  method  and  its  wide  application 
in  the  different  departments  of  zoological  investiga- 
tion is  the  most  characteristic  recent  tendency  of 
zoology.  Zoological  investigation  has  successively 
advanced  from  the  stage  of  mere  observation  to  that 
of  comparison  and,  finally,  to  the  method  of  experi- 
mentation. 

The  greatest  present  activity  is  in  some  of  the 
more  recent  offshoots  of  zoology  such  as:  cytology, 


122     THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  experimental  study  of  heredity,  including  Men- 
delism,  neurology,  protozoology  and  parasitology, 
ecology,  animal  psychology  and  behavior,  paleo- 
zoology  and  economic  entomology.  Morphological 
investigations  on  broad  lines  have  been  largely  taken 
over  by  the  anatomists,  while  the  zoologists  are  more 
engaged  with  cytology,  ecology,  genetics,  etc. 

In  the  line  of  cellular  studies  (cytology)  there  has 
been  great  refinement  of  technique  and  of  observa- 
tion. The  minute  constitution  of  the  germinal  ele- 
ments and  of  the  cellular  phenomena  of  develop- 
ment have  been  worked  out,  the  physical  basis  of 
heredity  has  been  located  in  the  chromosomes  and, 
more  recently,  partly  within  the  cytoplasm  of  the 
egg.  These  studies  are  closely  allied  with  those  of 
experimental  embryology  in  which  so  many  advances 
are  being  made — the  nature  of  fertilization  as  a 
physiological  process,  etc. 

The  theory  of  sex-determination  and  the  biology  of 
twins  have  aspects  of  especial  interest  and,  recently, 
have  been  investigated  by  zoologists  with  important 
results. 

In  morphology,  studies  in  neurology  have  taken 
the  center  of  the  field.  Although  there  are  many 
individual  pieces  of  morphological  investigation  car- 


MAIN  PATHWAYS  AND  TENDENCIES     123 

ried  out  on  a  higher  plane  than  that  of  previous 
years,  investigations  of  the  architecture  of  the 
nervous  system  in  all  its  aspects  is  one  of  the  obvious 
recent  tendencies  of  zoology. 

Cooperation  in  neurological  research  is  a  promising 
sign,  made  by  the  association  of  Neurological  Insti- 
tutes in  a  tacitly  understood  program  of  investiga- 
tion. Some  of  the  Institutes  thus  cooperating  are 
those  of  Ludwig  Edinger  at  Frankfort  on  the  Main, 
of  Ariens  Kappers  of  Holland  and  of  the  Wistar 
Institute  of  Philadelphia.  In  the  United  States  the 
Wistar  Institute  of  Anatomy  and  Biology  is  especially 
devoted  to  researches  hi  Neurology  under  the  leader- 
ship of  Professor  H.  H.  Donaldson. 

Adjuncts. — Various  adjuncts  such  as  museums, 
zoological  gardens,  special  collections,  etc.,  have 
been  helpful  to  the  work  of  zoologists.  These  have 
been  of  service  in  the  dissemination  of  knowledge  of 
animals  among  the  masses,  but,  most  of  all,  they  have 
supplied  facilities  for  the  researches  of  specialists. 
Among  the  institutions  of  this  type  in  the  United 
States  may  be  mentioned  the  Agassiz  Museum  of 
Comparative  Zoology  at  Harvard  University,  the 
collections  at  Yale  University,  the  American  Mu- 
seum of  Natural  History  of  New  York  City,  the 


i24     THE  MAIN  CURRENTS  OF  ZOOLOGY 

Carnegie  Museum  at  Pittsburgh,  the  collections  of 
the  Philadelphia  Academy  of  Sciences,  the  National 
Museum  and  the  Smithsonian  Institution  at  Wash- 
ington. 

Zoological  gardens  exist  in  New  York,  Washing- 
ton, Philadelphia,  Chicago  and  at  other  places. 

The  embryological  collection  of  the  late  Dr.  Charles 
Sedgwick  Minot  of  Boston  and  of  Dr.  Franklin  P. 
Mall  (died  1917)  of  Baltimore  are  of  great  service  to 
investigators  in  embryology. 

The  entomological  bureau  at  Washington,  D.  C., 
and  several  of  the  State  Entomologists  have  done 
much  to  advance  and  to  spread  broadcast  the 
knowledge  of  Insects.  The  sumptuous  publications 
of  the  United  States  government  have  placed  in  hand 
many  valuable  reports  on  animal  life  and  animal  in- 
dustry. The  activities  and  publications  of  the 
United  States  Fish  Commission  are  also  notable. 


CHAPTER  XH 
A  CHAPTER  ON  INSECTS 

INSECTS  are  so  interrelated  with  general  topics  that 
a  chapter  on  insects  will  serve  to  further  illustrate  the 
progress  of  zoological  study. 

This  is  the  largest  group  of  animals,  there  being 
approximately  400,000  species  described  and  classi- 
fied and  there  are  many  not  named.  From  whatever 
point  of  view  these  animals  have  been  studied,  they 
have  awakened  interest  and  enthusiasm  among 
naturalists.  Those  who  devote  particular  attention 
to  this  field  of  study  are  designated  entomologists 
and  the  great  division  of  zoology  thus  set  apart  is 
designated  entomology. 

From  the  time  of  Malpighi  (1628-1694)  and 
Swammerdam  (1637-1680)  insects  have  been  ob- 
jects of  interest  and  of  especial  consideration  to  the 
minute  anatomists. 

In  their  life  histories  some  insects,  as  the  butter- 
flies, bees,  etc.,  exhibit  hi  the  clearest  fashion  and  in 
the  widest  range  the  phenomena  of  metamorphosis. 
Hatching  from  the  egg  in  a  form  different  from  the 

adult  many  of  these  annuals  pass  through  various 

125 


126     THE  MAIN  CURRENTS  OF  ZOOLOGY 

stages  of  moults  as  larvae,  then  enter  the  quiescent  or 
pupa  stage  and  emerge  from  the  cocoons,  or  cases,  as 
adults. 

In  reference  to  the  fertilization  of  flowers  insects 
exhibit  some  of  the  most  interesting  relations  of 
nature.  With  remarkable  adroitness  they  extract  the 
nectar  of  flowers,  and  at  the  same  time  carry  pollen 
from  flower  to  flower,  and  further  cross-fertilization. 
Often  there  are  especial  adaptations  in  structure  to 
promote  this  end. 

But  it  is  in  reference  to  their  habits  that  they  show 
the  most  extraordinary  display  of  instinctive  in- 
telligence and  complex  behavior.  Those  forms  as 
ants,  bees  and  social  wasps  living  in  social  com- 
munities, that  are  well  organized  as  to  divisions  of 
labor  and  concerted  action,  may  be  properly  re- 
garded as  animals  of  dominant  intelligence. 

The  French  entomologist  J.  H.  Fabre  (1823-1913) 
devoted  a  long  life  to  observation  of  insects  showing 
especial  aptitude  for  searching  out  their  habits. 
He  has  related  his  observations  in  voluminous  and 
charming  writings  which  reached  the  dimensions  of 
ten  volumes  under  the  title  of  Souvenirs  Entomolo- 
giques.  These  memoirs  have  been  translated  into 
English  and  have  had  a  wide  circulation.  Fabre 


A  CHAPTER  ON  INSECTS  127 

(Fig.  25),  on  account  of  his  talents  as  an  observer,  his 
gifts  as  a  writer  and  his  direct  appeal  to  a  non- 
technical audience  is  probably  more  widely  known 
than  any  other  entomologist.  Those  who  wish  to 
taste  the  flavors  of  this  charming  writer  on  natural 
history  are  recommended  to  look  into  his  volume  on 
The  Hunter-Wasps. 

Other  entomologists,  more  important  from  the 

% 

scientific  standpoint  and  who  have  addressed  only  a 
scientific  audience  are  less  generally  known. 

Obviously  it  would  be  out  of  keeping  to  attempt 
in  a  few  pages  to  treat  of  the  various  aspects  of  the 
large  and  complex  group  of  insects.  Accordingly, 
only  a  few  selected  topics  will  be  brought  briefly  un- 
der consideration. 

On  account  of  their  relation  to  the  transmission  of 
diseases  insects  have  become  of  world-wide  interest, 
and  those  topics  are  selected  that  best  illustrate  their 
connection  with  human  diseases.  These  are  Malaria, 
Yellow  Fever  and  Sleeping-sickness.  It  is  to  be  borne 
in  mind  that  there  are  other  human  diseases  trans- 
mitted through  the  agency  of  insects,  as  bubonic 
plague,  sometimes,  typhoid  fever,  etc.,  and  many 
animal  diseases  of  cattle,  horses  and  lower  animals. 

Malaria. — Let  us  become  acquainted  with  the 


128     THE  MAIN  CURRENTS  OF  ZOOLOGY 

circumstances  under  which  was  demonstrated  the 
transmission  by  insects  of  Malaria.  Malaria  is  a 
widely-spread  infectious  disease.  This  disease,  char- 
acterized by  periodically  recurring  chills  and  fever 
was  called  Malaria,  which  means  bad  air,  from  the 
belief  that  the  Malaria  was  due  to  miasmatic  vapors 
arising  from  swamps  and  marshes.  The  disease, 
formerly  called  fever  and  ague,  was  observed  to  be 
most  prevalent  in  marshy  districts  and  in  places  with 
standing  water.  It  is  now  known  that  this  is  owing  to 
the  fact  that  wet  places  supply  the  conditions  for  the 
nurture  of  the  mosquitoes  that  transmit  the  disease. 

That  it  is  transmitted  by  a  particular  kind  of 
mosquito  was  well  established  by  Ross  in  1898. 
There  were  several  steps  leading  up  to  this  final 
demonstration  each  one  of  which  is  an  interesting  bit 
of  biological  advance. 

It  was  in  1880  that  Laveran,  a  French  military 
surgeon,  then  serving  in  Algeria,  made  known  the 
presence  of  a  micro-organism  within  the  blood  of 
patients  suffering  from  malaria.  This  so-called 
plasmodium  is  a  microscopic  animal  (protozoan) 
parasite.  In  the  blood  of  an  infected  person  the 
minute  malarial  parasite  bores  its  way  into  a  red 
blood  corpuscle  and  feeds  and  grows  at  the  expense 


A  CHAPTER  ON  INSECTS  129 

of  the  protoplasm  of  the  corpuscle.  It  rapidly  grows 
and  divides  into  a  progeny  of  thirteen  to  eighteen 
small  spore-like  individuals  which  are  set  free  into  the 
blood  by  the  bursting  of  the  wall  of  the  blood  cor- 
puscle. This  sporulation  occurs  periodically  and 
corresponds  to  the  attacks  of  chills  followed  by  fever, 
which  attacks  are  intermittent,  depending  on  the 
life  cycle  of  the  parasite. 

There  are  two  varieties  liberated  into  the  blood 
stream,  those  in  largest  number  being  able  to  mul- 
tiply by  direct  division,  while  the  other  kind  consist 
of  germinal  elements  that  require  a  different  host  and 
a  different  set  of  conditions  in  order  to  unite  and 
complete  their  life  history.  Their  union  is  a  process 
of  fertilization  and  is  accomplished  in  the  blood  of  a 
mosquito,  in  which  animal  they  undergo  a  compli- 
cated development,  resulting  finally,  in  an  immense 
number  of  spore-like  individuals. 

The  history  of  the  first  kind  is  more  simple.  They 
bore  their  way  into  new  corpuscles  and  repeat  the 
changes  mentioned  above.  The  number  of  corpus- 
cles infested  is  continually  multiplying  so  that  soon 
the  blood  becomes  the  seat  of  a  prodigious  number  of 
the  malarial  parasites. 

The  rate  at  which  they  are  produced  varies  with 


130     THE  MAIN  CURRENTS  OF  ZOOLOGY 

different  species.  If  they  mature  and  produce  spores 
in  thirty-six  hours,  the  patient  has  chills  and  fever 
every  other  day — for  the  chills  and  fever  correspond 
to  the  period  of  sporulation  and  bursting  of  the 
corpuscles.  There  are  other  species  with  a  different 
period  of  growth  giving  rise  to  the  different  types  of 
malaria — the  three-day,  the  four-day,  etc.  Minute 
as  they  are  these  different  varieties  can  be  distin- 
guished under  the  microscope. 

The  question  of  how  the  parasite  gets  into  the 
blood  had  now  to  be  solved  as  a  step  in  tracing  the 
infection  to  its  source.  Suspicion  was  fastened  on 
the  mosquito  and  after  observations  by  several  in- 
vestigators it  was  finally  shown  in  1898  that  the  bite 
of  a  particular  species  of  spot-winged  mosquito 
transmits  Malaria.  (Grassi  had  previously  shown 
that  these  parasites  complete  a  part  of  their  life 
history  in  the  body  of  the  mosquito.)  The  scientific 
name  of  the  mosquito  is  Anopheles.  The  Culex  or 
common  house  mosquito  is  not  a  malaria  carrier. 
The  Anopheles  is  widely  distributed.  It  is  a  night- 
flier,  and  only  the  female  circulates,  sucks  blood,  and, 
when  infected,  transmits  the  disease. 

In  the  most  infected  districts  it  was  experimen- 
tally demonstrated  that  to  remain  in  well-screened 


A  CHAPTER  ON  INSECTS  131 

shelters  after  sundown  was  sufficient  to  protect 
against  infection.  Experiments  on  a  large  scale  were 
also  carried  on  in  the  most  infected  districts  of  the 
swampy  campana  of  central  Italy.  Camps  were 
constructed  in  these  unhealthy  districts  and  the 
persons  experimented  upon  were  divided  into  two 
groups  that  lived  under  similar  conditions — except 
that  one  group  was  protected  in  well-screened  rooms, 
though  freely  exposed  to  the  fogs  and  vapors  from 
the  marshes.  The  other  group  was  unprotected  by 
screens.  The  results  were  spectacular.  Those  pro- 
tected from  the  bites  of  mosquitoes  contracted  no 
fever  while  those  that  were  exposed  to  mosquito  bites 
were  stricken  with  malaria. 

As  a  further  experiment  infected  mosquitoes  were 
sent  from  Rome  to  London  and  there  allowed  to  bite 
healthy  person  who  were  by  this  means  infected  with 
malaria  fever.  Thus  was  forged  the  last  link  in  the 
chain  of  evidence  connecting  the  Anopheles  mosquito 
with  the  transmission  of  malarial  fever. 

This  was  the  first  demonstration  of  direct  connec- 
tion between  insects  and  the  transmission  of  a 
specific  disease.  Although  suggestions  that  insects 
act  as  disease  carriers  are  found  scattered  through 
scientific  literature  for  a  number  of  years,  neverthe- 


132     THE  MAIN  CURRENTS  OF  ZOOLOGY 

less,  experimental  evidence  proving  the  truth  of  the 
theory  was  lacking.  Dr.  Manson  (later  Sir  Patrick) 
in  1880  was  the  first  to  show  that  the  blood  of  human 
beings  may  become  infected  with  a  worm-like  par- 
asite (Filaria  sanguinis)  by  the  bites  of  a  mosquito. 
Others  as  Dr.  A.  F.  A.  King  (1883)  contended  on 
theoretical  grounds  that  mosquitoes  carry  malaria 
but  adduced  no  experimental  evidence.  It  was  in 
1894  that  Manson  communicated  his  theory  con- 
cerning mosquitoes  to  Major  Donald  Ross  of  the 
British  army  and  on  this  suggestion  he  began  working 
on  malaria  in  India.  For  more  than  two  years  his 
results  were  negative  because  he  worked  on  the 
mosquito  Culex — but,  turning  his  attention  to 
Anopheles,  he  was  soon  able  to  trace  in  this  form  part 
of  the  life  cycle  of  the  malaria  parasite.  Many  ob- 
servers had  a  part  in  bringing  the  demonstration  to  a 
conclusion.  Grassi,  the  Italian,  did  important  work 
(1894),  but  Ross,  with  the  assistance  of  suggestions 
from  the  work  of  others,  and  utilizing  their  partial 
results,  was  able  to  demonstrate  so  completely  that 
the  malarial  parasite  is  transmitted  to  human  beings 
through  the  bite  of  a  particular  kind  of  mosquito, 
that  credit  for  this  great  discovery  is  usually  ac- 
corded to  him. 


A  CHAPTER  ON  INSECTS  133 

His  observations  afford  a  typical  example  of  the 
method  of  zoological  research — a  combination  of 
observation,  of  experiment  and  of  discerning  deduc- 
tion derived  from  the  results  of  the  complex  and 
involved  relations.  Several  steps  were  necessary  to 
reach  the  final  conclusion: 

1.  The  discovery  of  the  micro-organism  in  man  by 
Laveran  in  1880. 

2.  Tracing  the  life  history  of  this  germ  showing 
that  only  a  part  of  its  life  cycle  is  carried  on  in  the 
human  body  and  that  another  part  is  in  the  body  of 
the  Anopheles  mosquito. 

3.  Demonstrating  that  the  bites  of  an  infected 
Anopheles  mosquito  transmits  the  disease. 

4.  Camp  experiments  showing  that  it  is  not  due  to 
other  causes. 

Malaria  cannot  be  contracted  by  contact  with  an 
infected  patient,  nor  through  the  inhalation  of  va- 
pors of  swamps.  The  question  now  arises,  how  does 
a  mosquito  become  infected?  When  a  mosquito 
sucks  blood  from  a  person  suffering  from  malarial 
fever  it  draws  into  its  body  blood  containing  the 
parasite  (the  second  variety  mentioned  that  repro- 
duce by  fertilization)  some  of  which  are  in  a  con- 
dition to  conjugate.  These  forms  conjugate  and 


134     THE  MAIN  CURRENTS  OF  ZOOLOGY 

undergo  a  development  in  the  walls  of  the  stomach 
of  the  mosquito.  The  conjugation  is  a  sort  of  fer- 
tilization such  as  occurs  in  all  animals  and  plants,  but 
it  will  not  take  place  in  human  blood.  A  "  secondary 
host"  is  necessary  in  which  to  complete  the  life 
cycle.  After  fertilization  the  developing  forms  pro- 
duce nodules  on  the  walls  of  the  stomach  of  the 
mosquito  and  in  these  nodules  takes  place  the 
transformation  into  spindle-shaped  forms  which  get 
into  the  salivary  ducts  of  the  mosquito.  When 
biting,  the  mosquito  injects  some  of  these  into  the 
blood  of  the  victim  and  there  they  begin  to  multiply 
rapidly  by  asexual  budding. 

Doses  of  quinine  are  used  to  kill  the  malarial 
parasite. 

Studies  of  the  development  of  the  mosquito  soon 
led  to  methods  of  protection.  Mosquitoes  breed  in 
water — a  small  quantity  being  sufficient .  Protection 
comes  from  draining  marshes,  getting  rid  of  pools  and 
of  containers  of  exposed  water,  and  from  spraying 
with  crude  petroleum  so  that  the  wigglers  which 
hatch  from  the  eggs  can  not  get  air,  and  conse- 
quently, the  mosquito  can  not  come  to  its  full  devel- 
opment. The  use  of  screens  and  remaining  indoors 
after  sundown  are  also  wise  measures  of  precaution. 


A  CHAPTER  ON  INSECTS  135 

These  methods  have  cleared  malarial  regions  of 
the  sources  of  infection  and,  in  particular,  in  the 
Panama  zone,  conditions  were  established  that  made 
possible  the  construction  of  the  Panama  Canal. 

Yellow  Fever. — There  is  no  more  interesting  and 
inspiring  chapter  of  biological  achievements  than 
that  of  the  struggle  and  the  triumph  of  demon- 
strating the  nature  and  the  means  of  conveyance  of 
yellow  fever.  This  is  one  of  the  greatest  medical 
discoveries  of  any  century.  It  is  usually  designated 
the  greatest  American  medical  discovery — but,  it 
stands  in  parity  with  another  medical  advance  orig- 
inating in  the  United  States,  viz.,  painless  surgery,  ac- 
complished by  means  of  the  administration  of  ether. 

Yellow  fever  is  a  rapidly  spreading,  most  dreaded 
and  very  fatal  disease  of  tropical  and  sub-tropical 
climates.  Havana  and  Gulf  ports  have  repeatedly 
been  the  scene  of  this  great  scourge.  Up  to  1898  it 
was  believed  to  be  communicated  by  infected  articles 
of  clothing,  bedding,  furniture,  etc.,  and,  further, 
that  it  was  commonly  introduced  into  the  body 
through  respiration.  But,  thanks  to  the  investiga- 
tions of  Walter  Reed  and  his  associates,  it  is  now 
thoroughly  demonstrated  that  yellow  fever  is  trans- 
mitted through  the  bite  of  a  mosquito  and  in  no 


136     THE  MAIN  CURRENTS  OF  ZOOLOGY 

other  way.  Just  as  malaria  is  always  transmitted  by 
mosquitoes  of  the  Anopheles  variety  so  also  is  yellow 
fever  carried  by  another  mosquito  of  the  genus 
Stegomyia. 

In  the  year  1900,  President  McKinley  appointed 
Dr.  Walter  Reed  (Fig.  26)  as  chairman  of  a  com- 
mittee to  proceed  to  Havana  for  the  study  of  in- 
fectious diseases — more  especially  yellow  fever.  In 
about  six  months  after  his  arrival  he,  with  the 
assistance  of  his  associates,  had  shown  that  yellow 
fever  is  transmitted  only  by  the  bite  of  a  particular 
kind  of  mosquito. 

Some  of  his  results  summarized  are  as  follows: 

1.  The  virus  or  germ  exists  for  the  first  three  days 
in  the  blood  of  the  sick  before  it  is  capable  of  pro- 
ducing infection. 

2.  A   mosquito   of   a   single   species — Stegomyia 
fasciata — becomes  infected  by  sucking  blood  from  a 
sick  person,  and  after  twelve  days  have  elapsed  (and 
thereafter)  can  carry  the  disease. 

3.  There  is  no  other  way  of  infection. 

Reed's  work  is  another  illustration  of  the  power  of 
applied  intelligence  guided  by  scientific  observation. 

The  essential  steps  involved  in  this  discovery  are 
similar  to  those  in  the  investigation  of  malaria: 


FIG.  25. — J.  HENRI  FABRE 
(1823-1913) 


FIG.  26. — WALTER  REED  (1851-1902) 

From  H.  A.  Kelly's  Walter  Reed  and 

Yellow  Fever 


FIG.  27.— W.  T.  G.  MORTON  (1819-1868) 

From  Camac's  Epoch-Making  Contributions 

to  Medicine 


FIG.  28. — EDWARD  JENNER 
(1749-1823) 


A  CHAPTER  ON  INSECTS  137 

1.  The  particular  organism  producing  the  disease 
is  not  known — probably  because  it  is  too  small  for 
microscopic  observation.    Nevertheless,  it  is  demon- 
strated that  there  is  something  in  the  blood  that 
produces  the  disease.    This  something  is  assumed  to 
be  of  animal  nature — owing  to  the  requirement  of 
two  hosts  and  a  relatively  long  tune  to  complete  its 
cycle.    For  want  of  a  better  name  it  is  designated  a 
virus. 

2.  The  demonstration  that  it  can  not  be  trans- 
mitted by  clothing,  bedding,  contact  with  the  sick 
nor  through  the  atmosphere.    Prior  to  1898  it  was 
generally  believed  that  these  were  sources  of  infection 
but  two  young  privates  of  the  United  States  army — 
John  R.  Kissinger  and  J.  J.  Moran — volunteered  to 
put  the  question  to  a  practical  test,  and  for  twenty 
nights  they  slept  in  contact  with  bedding  and  night 
clothing  removed  from  those  sick  and  dying  with 
yellow  fever.    No  contagion  followed  and  thus  it  was 
proved  that  the  disease  can  not  be  conveyed  in  this 
manner.    This  service  to  the  cause  of  science  by  these 
two  men  involved  great  courage  and  high  devotion  to 
the  cause  of  humanity. 

3.  Experimental    evidence    that,    on    the    other 
hand,  yellow  fever  is  transmitted  by  the  bite  of 


138      THE  MAIN  CURRENTS  OF  ZOOLOGY 

the  mosquito  Stegomyia.  John  Moran  of  the 
United  States  army  submitted  to  the  bite  of  an  in- 
fected mosquito — as  a  result  he  was  stricken  with  the 
disease  but  recovered.  Dr.  Lazear,  one  of  Reed's 
assistants,  was  accidentally  bitten  by  a  mosquito  and 
died  of  yellow  fever.  The  circumstances  attending 
both  these  cases  were  such  that  no  doubt  existed  as 
to  the  direct  connection  between  the  bite  of  the 
infected  mosquitoes  and  the  disease. 

Reed  appreciated  the  significance  of  his  discovery, 
and  in  the  first  enthusiasm  of  the  demonstration  he 
wrote  this  intimate  estimate  to  his  wife:  "Rejoice 
with  me,  sweetheart,  as  aside  from  the  antitoxin  of 
diphtheria  and  Koch's  discovery  of  the  tubercule 
bacillus,  it  will  be  regarded  as  the  most  important 
piece  of  work,  scientifically,  during  the  nineteenth 
century." 

The  results  of  the  demonstration  were  immediate 
and  far  reaching.  Havana  and  Gulf  ports  were 
practically  freed  from  the  disease.  Indeed,  since 
1901,  Havana,  formerly  the  favorite  home  of  this 
deadly  disease,  has  been  exempt  from  its  ravages. 

Sleeping  Sickness. — The  third  of  these  biological 
studies  of  insects  and  transmission  of  diseases  in- 
volves the  sleeping  sickness.  The  sleeping  sickness 


A  CHAPTER  ON  INSECTS  139 

is  a  strange  mysterious  disease  characterized,  as  the 
disease  progresses,  by  lethargy  and  a  somnolescence 
which  terminates  fatally. 

It  had  long  been  known  on  the  western  coast  of 
Africa,  but,  in  1901  a  virulent  outbreak  occurred  in 
central  Africa,  in  the  Uganda  district  and  along  the 
shores  of  Lake  Victoria  Nyanza.  The  disease  killed 
so  many  that  the  British  government  undertook  to 
investigate  the  causes  of  the  disease  and  to  seek  a 
remedy.  The  wide-spread  nature  of  this  epidemic  in 
which  200,000  died  in  one  year  compelled  notice. 
Colonel  Bruce  of  the  British  navy,  who  was  expe- 
rienced in  the  investigation  of  infectious  diseases, 
was  sent  there  in  1903  to  hives tigate  the  conditions 
and  the  characteristics  of  the  disease. 

As  in  the  case  of  malaria  and  yellow  fever  it  took 
the  highest  qualities  of  scientific  observation  to 
discover  the  particular  organism  of  the  disease  and 
to  find  out  the  way  in  which  it  is  transmitted. 
Colonel  Bruce  had  the  problem  to  work  out,  of  the 
nature  and  the  mode  of  infection  of  sleeping  sickness. 
He  determined  that  as  to  its  nature,  it  is  produced  by 
the  presence  in  the  blood  and  the  cerebro-spinal 
fluid  of  a  cork-screw  shaped  parasite — a  minute 
animal  organism  somewhat  longer  than  the  diameter 


i4o     THE  MAIN  CURRENTS  OF  ZOOLOGY 

of  a  blood  corpuscle.  This  organism  is  sharp  pointed 
at  each  end  and  is  provided  with  a  vibratile  mem- 
brane and  a  fiagellum  which  produce  motion.  This 
parasite — called  a  trypanosome — was,  by  Bruce  and 
other  observers,  found  in  the  blood  and  spinal  fluid 
as  a  constant  concommitant  of  the  disease. 

Its  mode  of  transmission  was  obscure  and  a 
problem  of  great  difficulty.  Studies  on  the  wild  and 
domesticated  animals  of  the  district  were  a  means  of 
throwing  light  on  the  matter.  Similar  protozoan 
parasites  were  known  to  infect  domesticated  animals 
and  to  live  in  the  blood  of  native  wild  animals  such 
as  the  antelope,  buffalo,  and  others.  These  wild 
animals  having  been  long  infested  with  these  par- 
asites had  acquired  a  tolerance  for  them  and  re- 
mained unharmed,  but  recently  infected  domesti- 
cated animals  were  not  immune.  These  parasites 
were  shown  to  be  conveyed  by  the  bite  of  a  tsetse-fly 
from  the  wild  game  inhabiting  the  district — in  whose 
blood  they  produce  no  deleterious  result — to  the 
annuals  that  were  susceptible  to  poisons  produced 
by  the  parasites.  By  analogy,  suspicion  was  fastened 
on  the  tsetse-fly  as  the  probable  source  of  transmis- 
sion, but  it  was  a  very  difficult  matter  to  prove  it.  In 
searching  for  the  agent  of  the  transmission  of  human 


A  CHAPTER  ON  INSECTS  141 

sleeping  sickness,  Bruce  had  the  help  of  many  native 
collectors  who  were  paid  to  bring  to  his  camp  the 
various  flies  and  other  insects  of  the  district.  Finally, 
the  source  of  transmission  was  fastened  on  a  par- 
ticular species  of  the  tsetse-fly — Glossina  palpalis. 
The  tsetse-flies  are  a  genus  of  flies  only  found  in 
Africa.  There  are  seven  species  known — the  par- 
ticular fly  that  transmits  sleeping  sickness  in  human 
beings  is  a  little  bigger  than  the  common  house  fly 
and  much  like  it  in  color. 

To  establish  an  undoubted  connection  between 
the  tsetse-fly  and  the  transmission  of  sleeping  sick- 
ness came  to  Bruce  as  a  triumph  of  scientific  observa- 
tion and  deduction.  Finding  that  monkeys  also  were 
susceptible  to  the  disease  he  caused  infected  flies  to 
bite  monkeys,  thus  producing  the  disease  and  dem- 
onstrating the  mode  of  its  transmission. 

In  1906,  a  sort  of  arsenic  aniline  (Atoxyl)  was 
found  by  Thomas  and  Breinl  to  be  helpful  in  some 
cases.  The  suggestion  of  this  substance  as  a  possible 
remedy  was  erroneously  ascribed  to  Robert  Koch 
who  merely  confirmed  the  observations  of  the  earlier 
investigators. 

To  avoid  a  common  confusion  it  may  be  well  at 
this  point  to  emphasize  the  fact  that  the  three 


I42     THE  MAIN  CURRENTS  OF  ZOOLOGY 

diseases  spoken  of  above  are  all  produced  by  animal 
organisms.  On  the  other  hand,  the  bacteria  whose 
pathogenic  qualities  have  been  known  so  long  are 
plants.  Thus,  typhoid  fever,  tuberculosis,  diphtheria, 
etc.,  are  produced  by  plant  parasites  and  malaria, 
sleeping  sickness,  and  probably  yellow  fever  are 
produced  by  minute  animal  organisms. 

Among  other  diseases  transmitted  by  insects  may 
be  mentioned  the  bubonic  plague,  by  the  bite  of  lice 
of  rats;  many  diseases  of  cattle,  by  bites  of  flies, 
ticks,  etc.  These  insects  pass  along  the  disease 
germs  which  they  have  derived  by  blood  sucking 
from  other  animals. 


CHAPTER  Xin 
THEORIES  OF  EVOLUTION 

THE  circumstances  surrounding  the  rise  of  evolu- 
tion theories  in  the  nineteenth  century  are  not  gen- 
erally understood.  There  is  a  wide-spread  belief 
that  the  theory  of  Charles  Darwin  was  first  in  the 
field,  and,  confusion  on  this  point  is  so  general  that 
whenever  organic  evolution  is  mentioned  many  peo- 
ple conclude  that  the  particular  hypothesis  of  Dar- 
win is  always  referred  to,  but  such  is  by  no  means  the 
case.  By  organic  evolution  is  meant  the  great  nat- 
ural process  through  which  animals  and  plants  have 
come  to  be  what  they  are — a  purely  historical  ques- 
tion of  what  has  happened  in  the  past  to  produce  the 
transmutation  of  animals  and  plants — in  a  word,  the 
discovery  of  the  lineage  of  living  organisms.  Dar- 
winism, on  the  other  hand,  is  one  explanation  offered 
to  account  for  the  evolution  of  animals  and  plants. 
Darwin  undertakes  to  designate  the  particular 
agency  that  has  been  at  work  in  nature  to  produce 
the  various  kinds  of  organisms.  Darwinism  refers 
specifically  to  the  action  of  natural  selection  as  the 

chief  agent  in  bringing  about  organic  evolution. 

143 


144      THE  MAIN  CURRENTS  OF  ZOOLOGY 

To  Lamarck,  the  eminent  French  zoologist,  be- 
longs recognition  as  the  founder  of  the  doctrine  of 
organic  evolution,  fifty  years  before  the  publication 
of  Darwin's  great  book,  The  Origin  of  Species.  It  is 
true,  however,  that  the  publication  of  Darwin's  book 
was  the  means  that  brought  the  matter  prominently 
before  the  world  and  started  the  vigorous  contro- 
versy regarding  the  truth  or  falsity  of  the  theory. 

There  are  four  theories  of  organic  evolution  that 
have  received  a  large  amount  of  attention  from 
naturalists  in  addition  to  several  supporting  and 
some  rival  theories.  No  one  can  be  adequately  in- 
formed on  the  matter  who  does  not  take  the  trouble 
to  get  an  idea  of  the  prominent  features  of  these 
theories  and  their  relation  to  one  another.  The  four 
theories  referred  to  are  those  of  Lamarck,  Darwin, 
Weismann,  and  De  Vries. 

Lamarck. — Although  the  evolutionary  point  of 
view  had  been  vaguely  suggested  at  different  times 
prior  to  Lamarck,  he  was  the  first  to  announce  a 
comprehensive  theory  of  organic  evolution  that  has 
maintained  to  the  present  time  a  creditable  standing 
in  the  intellectual  world.  His  immediate  predeces- 
sors, Buffon,  Goethe,  and  Erasmus  Darwin  (grand- 
father of  Charles  Darwin),  dealt  with  the  same  great 


THEORIES  OF  EVOLUTION  145 

theme  but  much  less  rigorously  than  Lamarck.  The 
earlier  theories  were  either  too  vague  and  discursive 
or  too  inadequate  to  serve  as  foundations.  La- 
marck's theory  was  so  much  more  thoroughly  thought 
out  that  it  completely  superseded  all  earlier  attempts 
and  marks  the  beginning  of  evolutionary  thought  in 
its  modern  sense. 

Lamarck  (Fig.  29)  first  gave  expression  to  his 
evolutionary  ideas  in  1800,  in  an  introductory  lecture 
to  a  course  of  instruction  regarding  the  invertebrates. 
This  was  published  in  1801.  The  theory  was  some- 
what elaborated  in  the  years  1802,  1803,  and  1806. 
Finally,  it  was  fully  expounded  in  Philosophic 
Zoologiquej  in  1809,  and  that  year  marks  the  first 
distinct  epoch  in  the  rise  of  evolutionary  thought. 

In  this  book  he  sets  forth  the  basis  of  his  con- 
clusions. He  ascribes  to  the  effects  of  use  and  disuse 
the  various  modifications  of  organic  structures — use 
tending  to  increase,  and  disuse  to  decrease  the  size 
and  efficiency  of  organs.  The  changes  thus  pro- 
duced, by  organisms  adapting  themselves  to  the  con- 
ditions under  which  they  live,  were  supposed  by 
Lamarck  to  be  directly  inherited  and  improved  (or 
further  decreased)  in  succeeding  generations. 

It  appears,  he  says:  "that  time  and  favorable  con- 


146     THE  MAIN  CURRENTS  OF  ZOOLOGY 

ditions  are  the  two  principal  means  which  nature  has 
employed  in  giving  existence  to  all  her  productions.'7 
When  surrounding  conditions  are  stable  the  evolu- 
tionary process  reaches  a  stage  of  equilibrium,  but, 
when  the  environment  varies  (or  new  needs  arise), 
the  new  conditions  of  life  impress  themselves  on  the 
plastic  organisms  and  they  become  altered  to  better 
adapt  themselves  to  these  new  conditions.  His 
theory  as  set  forth  was  comprehensive  and  included 
the  evolution  of  the  human  body  as  well  as  all  other 
organisms. 

Adaptation  of  organisms  to  environment,  in  gen- 
eral and  in  detail,  producing  changes  of  structure 
through  use  and  disuse  of  organs  and  the  direct  in- 
heritance of  the  modifications  is  a  simplified  state- 
ment of  Lamarck's  theory. 

Until  Lamarck  was  fifty  years  of  age  he  was  a 
botanist  and  had  secured  a  lasting  reputation  in  that 
field,  but,  in  1894,  when  the  Jar  dm  des  Plantes  was 
reorganized  he  was  appointed  to  a  position  in  Zoology 
in  charge  of  the  invertebrates.  Apparently,  it  was 
the  observations  he  made  in  connection  with  these 
new  duties  that  led  to  the  formulation  of  his  theory. 
At  this  time  the  belief  was  current  that  species  are 
unalterable.  The  dogma  of  the  fixity  of  species 


FIG.  29. — J.  B.  LAMARCK  (1744-1829) 
From  Thornton's  British  Plants,  1805 


THEORIES  OF  EVOLUTION  147 

prevailed.  Linnaeus  had  announced  himself  in  favor 
of  the  idea,  and,  so  generally  was  his  authority  recog- 
nized, that  scarcely  anyone  thought  of  bringing  it 
into  question.  But  Lamarck  saw  that  species  vary 
in  a  state  of  nature  to  such  an  extent  that  they  pass 
beyond  the  limits  that  can,  in  reason,  be  assigned  to 
species. 

Lamarck's  theory,  although  so  definite,  did  not 
find  a  foothold  during  his  lif etime  and  the  fifty  years 
between  1809,  when  his  book  was  published,  and 
1859,  when  Darwin's  Origin  of  Species  appeared,  was 
characterized  by  the  temporary  disappearance  of 
the  theory  of  organic  evolution.  His  ideas  were 
ridiculed  by  Cuvier  and  were  practically  laughed  out 
of  court.  Charles  Darwin  also  paid  little  heed  to 
Lamarck  as  a  predecessor.  But,  it  is  a  significant 
circumstance  that,  nearly  a  century  after  being 
promulgated,  Lamarck's  principle  of  use-inheritance 
and  the  beginning  of  variations  should  have  been 
revived,  and,  under  the  title  of  Neo-Lamarckism, 
should  occupy  such  a  prominent  place  in  the  discus- 
sions regarding  the  factors  of  organic  evolution  that 
are  being  carried  on  at  the  present  time.  The  re- 
vival of  Lamarckism  is  especially  owing  to  the 
paleontological  investigations  of  Cope,  Hyatt  and 


148      THE  MAIN  CURRENTS  OF  ZOOLOGY 

others.  The  work  of  E.  D.  Cope,  in  particular,  led 
him  to  attach  importance  to  the  effects  of  mechanical 
and  other  external  causes  in  producing  variations  in 
animal  structure,  and  he  has  pointed  out  many  in- 
stances of  use-inheritance. 

Lamarck's  theory  was  founded  on  two  sets  of 
facts — those  of  variation  and  heredity.  These  are 
essential  to  any  theory  of  transmutation  of  species. 
Lamarck  undertook  to  account  for  variation  through 
the  influence  of  environment  during  the  lifetime  of 
the  individual,  and  the  direct  inheritance  of  these 
purposeful  variations  was  assumed.  This  is  the  in- 
heritance of  acquired  characters  which  as  we  shall  see 
was  vigorously  opposed  by  Weismann. 

Darwin. — Darwin's  theory  is  based  on  three  sets 
of  facts — variation,  heredity,  and  natural  selection. 
Two  of  the  factors  are  the  same  as  those  of  Lamarck 
but  they  were  treated  differently  by  Darwin.  La- 
marck undertook  to  assign  causes  for  variation. 
Darwin  (Fig.  5)  accepted  variation  and  assumed  that 
there  is  continually  occurring  in  living  organisms 
many  small  fluctuations  in  structures.  Naturally 
many  of  these  small,  fortuitous,  variations  would 
be  swamped,  but,  obviously,  some  of  them  are  re- 
tained and  improved  upon.  His  reply  to  the  ques- 


THEORIES  OF  EVOLUTION  149 

tion:  "What  particular  variations  will  be  perpet- 
uated?" was,  "only  those  that  prove  of  benefit  to 
the  race  in  the  struggle  for  existence  and  in  adapting 
themselves  to  environment. ' '  The  chance  inheritance 
cf  the  multitudinous  variations  would  produce 
chaotic  results  unless  directed  by  some  agency  and 
this  directing  agency  was  designated  by  Darwin, 
Natural  Selection.  This  is  the  central  idea  of  Dar- 
win's theory  and  the  essentially  new  factor  that  he 
added  tb  the  discussion.  He  observed  the  changes 
produced  by  artificial  selection  under  domestication 
of  animals  and  cultivation  of  plants.  Certain  varia- 
tions are  selected  by  breeders  and  agriculturalists  to 
be  bred  intensively,  and,  by  this  means,  marked 
changes  are  produced  in  pigeons,  poultry,  dogs,  cat- 
tle, flowers,  etc.  Now  since  these  changes  are 
obviously  the  result  of  a  process  of  selection  on  the 
part  of  man,  Darwin  concluded  that  conditions  exist 
in  nature  which  lead  to  the  selection  of  certain 
variations  to  survive  and  to  the  suppression  of  others. 
Some  such  assumption  is  necessary,  because  there 
is  a  tendency  to  overproduction  in  animals  and 
plants,  leading  to  a  struggle  for  existence,  and,  the 
determination  of  survival,  would  scarcely  be  a  matter 
of  chance.  One  illustration  will  suffice  to  carry  the 


ISO     THE  MAIN  CURRENTS  OF  ZOOLOGY 

idea.  A  single  trout,  for  illustration,  lays  from 
60,000  to  100,000  eggs.  If  the  majority  of  these 
arrived  at  maturity  and  gave  rise  to  progeny,  the 
next  generation  would  present  a  prodigious  number, 
and  the  numbers  in  succeeding  generations  would 
increase  so  rapidly,  that  soon  there  would  not  be 
room  in  the  fresh  waters  of  the  earth  to  contain  their 
descendants.  It  is  true  that  most  animals  produce 
fewer  eggs  (some  lay  more),  but  observation  estab- 
lishes the  truth  that  animals  tend  to  multiply  by 
geometric  progression,  while  as  a  matter  of  fact  the 
number  of  any  one  kind  remain  practically  constant. 

The  agency  that  determines  which  organisms  shall 
be  preserved  in  the  struggle  for  existence  is  natural 
selection.  This  agency  will  favor  certain  variations 
in  structure  that  may  prove  of  advantage,  so  that, 
in  the  long  run,  those  best  adapted  to  conditions  of 
life  would  survive. 

Natural  selection  works  in  such  a  variety  of  ways 
that  a  few  illustrations  are  essential.  Fleetness  in 
such  animals  as  antelopes  may  be  the  particular 
thing  which  secures  their  safety.  In  all  kinds  of 
strain  due  to  scarcity  of  food,  inclemency  of  weather 
and  other  rigorous  conditions,  those  forms  with  the 
best  powers  and  physiological  resistance  will  have 


THEORIES  OF  EVOLUTION  151 

the  best  chance  to  survive.  The  keen  vision  of  birds 
of  prey,  such  as  hawks,  will  be  a  factor  in  their 
preservation.  Those  hawks  that  are  born  with  weak 
or  defective  vision  cannot  cope  with  the  conditions 
under  which  they  get  their  food.  Natural  selection 
compels  the  eye  to  come  up  to  a  certain  standard  and 
the  conditions  of  living  maintains  the  standard. 
Certain  animals  are  protected  from  their  enemies 
by  being  inconspicuous — conforming  to  the  colors 
of  the  background  on  which  they  live — resembling 
twigs  and  other  natural  objects.  In  other  cases, 
especially  among  insects,  flaming  colors  give  warning 
that  the  animals  are  of  noxious  taste  and  their 
pursuers  learn  to  leave  them  alone.  An  illuminating 
instance  of  the  action  of  natural  selection  is  the 
production  of  weak-winged  beetles  from  strong- 
winged  ancestors.  In  very  windy  islands  the  strong- 
winged  forms  being  more  in  the  air  and  flying  further 
from  protection  are  blown  out  to  sea.  The  weak- 
winged  are  better  adapted  to  these  particular  con- 
ditions, and,  natural  circumstances  tend  to  favor 
them  and  to  operate  against  the  strong-winged 
individuals.  This  makes  one  point  clear — natural 
selection  tends  to  adapt  animals  to  their  conditions  of 
life  and  results,  not  always,  in  the  survival  of  the 


iS2     THE  MAIN  CURRENTS  OF  ZOOLOGY 

best,  that  is  the  ideally  perfect,  but  in  the  survival  of 
the  fittest.  A  similar  instance  is  found  in  the  sup- 
pression of  certain  sets  of  organs  in  internal  parasites. 
The  organs  of  digestion,  not  being  necessary  under 
their  condition  of  life,  are  suppressed,  but  the  repro- 
ductive organs,  upon  which  continuance  of  the  race 
depends,  are  greatly  increased.  These  illustrations 
will  assist  in  giving  an  idea  of  what  Darwin  meant  by 
natural  selection. 

One  other  point  should  be  emphasized.  Darwin, 
who  was  one  of  the  most  candid,  sincere  and  straight- 
forward of  men,  did  not  claim  that  natural  selection 
was  the  only  natural  agency  but  merely  the  chief  one 
in  bringing  about  evolution. 

Darwin's  theory  met  with  a  very  different  recep- 
tion from  Lamarck's.  It  received  immediate  atten- 
tion. It  was  vigorously  attacked  and  defended  and 
was  ultimately  accepted.  The  contrast  was  so 
great  that  naturally  the  inquiry  arises — Why?  It 
was  promulgated  more  than  fifty  years  after  La- 
marck's announcement  and,  in  the  meantime,  the 
way  had  been  prepared  by  the  publication  of  Lyell's 
Principles  of  Geology  (1830),  by  Chambers'  Vestiges 
of  Creation  (1844),  by  Herbert  Spencer's  writings 
regarding  the  reasonableness  of  the  hypothesis  of 


THEORIES  OF  EVOLUTION  153 

development  (1852)  and  by  other  writers.  The  times 
were  more  favorable  for  launching  the  great  idea  of 
evolution.  But  the  wide  currency  which  the  idea 
immediately  attained  was  chiefly  owing  to  Darwin's 
exposition  of  the  idea  of  natural  selection.  He 
designated  explicitly  a  natural  cause  for  the  changes 
in  animals  that  had  heretofore  been  so  perplexing. 
Even  the  masses  could  understand  his  argument. 
The  character  of  his  first  publication  (Origin  of 
Species,  1859)  was  also  such  as  to  attract  attention 
and  secure  respect.  He  had  been  at  work  on  his 
theory,  experimenting  and  observing,  for  more  than 
twenty  years,  and  his  publication  showed  that 
quality  of  thoroughness,  fairness  and  ripeness  that 
commanded  consideration. 

Among  those  who  assisted  in  the  spread  of  the 
Darwinian  theory  amongst  English-speaking  people, 
Thomas  Henry  Huxley  (Fig.  31)  stood  preeminent. 
Darwin  was  of  pacific  disposition  while  Huxley  was 
aggressive  and  both  ready  and  forceful  in  public 
debate.  He  became  the  recognized  champion  of  the 
theory  of  descent,  and  vigorously  and  effectively  de- 
fended it  against  attack. 

It  is  an  interesting  circumstance  that  Alfred  Rus- 
sell Wallace  (1823-1913),  by  a  flash  of  insight,  had 


154     THE  MAIN  CURRENTS  OF  ZOOLOGY 

arrived  independently  at  the  idea  of  struggle  in 
nature,  with  the  survival  of  the  fittest  through 
natural  selection.  He  communicated  these  ideas  to 
Mr.  Darwin  in  1858,  and,  with  high-minded  gen- 
erosity, Darwin  was  disposed  to  allow  the  credit  to 
go  to  Mr.  Wallace,  withholding  his  own  publication 
upon  which  he  had  been  working  for  so  many  years. 
He  was  pursuaded  to  leave  the  matter  in  the  hands 
of  two  of  his  friends,  Sir  Charles  Lyell  and  Joseph 
Hooker,  who  arranged  for  the  publication  simulta- 
neously, of  manuscript  sketches  of  Darwin,  made  in 
1839,  1844  and  1857,  and  the  essay  of  Wallace  pre- 
pared in  1858.  Although  Darwin  was  so  punctilious 
about  having  his  friend,  Wallace,  receive  a  share  of 
the  credit,  Wallace  himself  has  insisted,  and  the 
world  has  recognized,  that  the  credit  for  the  natural 
selection  theory  belongs  essentially  to  Darwin. 

Weismann. — The  theory  of  Weismann  is  more 
complex  and  is  difficult  to  state  with  brevity  and 
lucidity.  It  will  dispel  a  wide-spread"  confusion 
regarding  his  theory  to  say,  at  once,  that  he  is  a 
Darwinian — the  recognized  leader  of  the  Neo- 
Darwinians.  He  carried  the  idea  of  natural  selection 
further  than  Darwin  did,  extending  it  to  the  tissues 
and  even  to  the  minute  vital  elements  of  the  cell.  It 


THEORIES  OF  EVOLUTION  155 

is  to  be  understood,  therefore,  that  as  regards  Dar- 
winism, his  is  a  supplementary  or  supporting  theory 
and  not  a  replacing  theory. 

It  is  complex  and  involves  assumptions  as  to  the 
behavior  of  a  number  of  hypothetical  vital  units, 
designated  by  Weismann:  idants  (chromosomes);  ids 
(chromomeres),  determinants,  and  biophors  (the 
elementary  vital  units).  Two  of  these,  the  ids  and 
the  idants  are  visible  under  the  microscope,  but  the 
determinants  and  the  biophors  are  too  minute  to  be 
rendered  visible. 

His  theory  of  evolution  is  in  reality  the  outcome  of 
his  theory  of  heredity,  designated  the  "Continuity 
of  germ-plasm, "  and  to  comprehend  his  reasoning  it  is 
necessary  to  understand  what  is  meant  by  the  germ- 
plasm  and  by  its  continuity. 

As  is  well  known,  animals  and  plants  arise  from 
germinal  elements  of  microscopic  size;  these  are,  in 
plants,  the  spores,  the  ovules  and  their  fertilizing 
agents;  and,  in  animals,  the  eggs  and  the  sperms. 
Now,  since  all  animals,  even  the  highest,  begin  their 
existence  as  a  fertilized  egg,  that  structure,  minute  as 
it  is,  must  contain  all  hereditary  qualities,  because 
this  is  the  only  material  substance  that  passes  from 
one  generation  to  another.  This  formative  sub- 


156     THE  MAIN  CURRENTS  OF  ZOOLOGY 

stance  is  the  germ-plasm.  It  is  the  living  vital  sub- 
stance of  organisms  that  takes  part  in  the  develop- 
ment of  new  generations. 

Weismann  (Fig.  32)  points  out  that  the  many- 
celled  body  was  gradually  produced  by  evolution,  and 
that  in  the  transmission  of  life  by  the  higher  animals 
the  continuity  is  not  between  body-cells  and  their 
like,  but  only  between  germinal  elements,  around 
which  in  due  course  new  body-cells  are  developed. 
Thus  he  regards  the  body-cells  as  constituting  a  sort 
of  vehicle  within  which  the  germ-cells  are  carried. 
The  germinal  elements  contain  the  primordial  sub- 
stance around  which  the  body-cells  have  developed, 
and,  since  in  all  the  long  process  of  evolution  the 
germinal  elements  have  been  the  only  form  of  con- 
nection between  different  generations,  the  substance 
composing  them  has  unbroken  continuity. 

This  conception  of  the  continuity  of  the  germ- 
plasm  is  the  foundation  of  Weismann's  doctrine. 
It  is  one  of  the  most  fruitful  biological  ideas  devel- 
oped during  the  nineteenth  century,  and  it  replaced 
as  a  basis  all  earlier  theories  of  heredity.  Although 
Weismann  was  not  the  originator  of  the  idea  of 
germinal  continuity,  he  is  nevertheless  the  one  who 
has  developed  it  the  most  extensively. 


FIG.  30. — WILLIAM  HARVEY 
(1578-1657) 


FIG.  31. — THOMAS  H.  HUXLEY 
(1825-1895) 


FIG.  32. — AUGUST  WEISMANX 
(1834-1914) 


FIG.  33. — HUGO  DE  VRIES 


THEORIES  OF  EVOLUTION  157 

In  1893  there  was  published  an  English  translation 
of  his  famous  book  The  Germ-Plasm  which  stimulated 
so  much  discussion  among  biologists.  This  sets 
forth  his  theory  of  heredity.  For  many  years  Weis- 
mann  was  a  professor  in  the  University  of  Freiburg, 
and  his  lectures  on  the  evolution  theory  were  de- 
servedly famous  and  well  attended.  The  best 
exposition  in  English  of  his  theory  is  The  Evolution 
Theory,  published  in  two  volumes  in  1904.  In  the 
preface  he  says:  "I  make  this  attempt  to  sum  up  and 
present  as  a  harmonious  whole  the  theories  which  for 
forty  years  I  have  been  gradually  building  up  on  the 
basis  of  the  legacy  of  the  great  workers  of  the  past, 
and  on  the  results  of  my  own  investigations  and 
those  of  my  fellow-workers." 

Since  we  may  assume  that  there  has  been  unbroken 
continuity  of  the  germ-plasm  from  the  beginning,  we 
may  also  assume  that  its  organization  has  become 
very  complex.  Protoplasm  is  impressionable,  re- 
sponding to  various  forms  of  stimuli  and  undergoing 
modifications  in  response  to  environmental  influences. 
These  subtle  changes  occurring  within  the  proto- 
plasm affects  its  organization,  and,  in  the  long  run, 
it  is  the  summation  of  experience  that  determines 
what  a  particular  mass  of  protoplasm  shall  be  and 


158      THE  MAIN  CURRENTS  OF  ZOOLOGY 

how  it  will  behave  in  development.  Two  separate 
masses  of  protoplasm  differ  in  detail,  as  to  capabili- 
ties and  potentialities,  according  to  the  experiences 
through  which  they  have  passed,  and  no  two  will  be 
absolutely  identical. 

We  have  seen  that  variation  and  heredity  are  the 
two  primary  factors  of  evolution.  The  way  in  which 
Weismann  accounts  for  variation  among  the  higher 
animals  is  both  ingenious  and  interesting.  In  all 
higher  organisms  the  sexes  are  separate  and  repro- 
duction of  their  kind  involves  the  union  of  germinal 
elements  from  both  parents. 

As  previously  stated,  the  germinal  elements  in-' 
volved  are  ovules  and  pollen  of  plants  and  eggs  and 
sperms  of  animals.  In  animals,  the  egg  bears  all 
hereditary  qualities  from  the  maternal  side,  and  the 
sperm  those  from  the  paternal  side.  The  intimate 
mixture  of  these  in  fertilization  gives  great  possibil- 
ities of  variations  arising  from  the  different  com- 
binations and  permutations  of  the  vital  units  within 
the  germ-plasm. 

The  variations  once  started  will  be  fostered  by 
natural  selection. 

It  is  now  evident  that  if  we  follow  Weismann's 
conclusions  logically,  there  can  be  no  inheritance  of 


THEORIES  OF  EVOLUTION  159 

acquired  characters — that  is,  of  acquisition  made  by 
the  body-cells,  or  changes  arising  in  them,  during  the 
lifetime  of  the  individual.  None  of  the  body-cells  are 
transmitted  and  the  hereditary  qualities  must  all  be 
located  within  the  plasms  of  the  germ-cells. 

The  outstanding  features  of  Weismann's  theory 
are  as  follows: 

1.  The  germ-plasm  has  unbroken  continuity  from 
the  beginning  of  life. 

2.  Heredity  is  accounted  for  on  the  principle  that 
the  offspring  is  composed  of  some  of  the  same  stuff 
(germ-plasm)  as  its  parents.    The  body-cells  are  not 
inherited. 

3.  Consequently,  there  is  no  inheritance  of  ac- 
quired characters. 

4.  Variations  arise  from  the  union  of  the  germinal 
elements,  giving  rise  to  varied  combinations  and 
permutations  of  qualities  of  the  uniting  germ-plasms. 

5.  Weismann  adopts  and  extends  the  principle  of 
natural  selection. 

De  Vries. — Hugo  de  Vries  (Fig.  33),  director  of 
the  Botanical  Garden  in  Amsterdam,  has  experi- 
mented widely  with  plants,  especially  the  evening 
primrose  (CEnothera  Lamarckiana) ,  and  has  shown 
that  different  species  appear  to  rise  suddenly.  These 


160      THE  MAIN  CURRENTS  OF  ZOOLOGY 

sudden  variations  that  breed  true,  and  thus  give  rise 
to  new  forms,  he  calls  mutations.  This  indicates  the 
source  of  the  name  applied  to  his  theory. 

In  his  Die  Mutationstheorie,  published  in  1901,  he 
argues  for  the  recognition  of  mutations  as  the 
universal  source  of  the  variations  that  lead  to  species- 
formation.  Although  he  evokes  natural  selection 
for  the  perpetuation  and  improvement  of  variations, 
and  points  out  that  his  theory  is  not  antagonistic 
to  that  of  natural  selection,  it  is  nevertheless  di- 
rectly at  variance  with  Darwin's  fundamental  con- 
ception, that  slight  individual  variations  "are  prob- 
ably the  sole  differences  which  are  effective  in  the 
production  of  new  species"  and  that  "as  natural 
selection  acts  solely  by  accumulating  slight,  succes- 
sive, favorable  variations,  it  can  produce  no  great  or 
sudden  modifications." 

The  work  of  De  Vries  is  a  most  important  con- 
tribution to  the  study  of  the  origin  of  species,  and  is 
indicative  of  the  fact  that  many  factors  must  be 
taken  into  consideration  when  one  attempts  to 
analyze  the  process  of  organic  evolution.  His  ob- 
servations widen  the  field  of  exploration.  While  he 
has  demonstrated  that  species  may  arise  by  muta- 
tions, there  is  at  the  same  time  good  evidence — from 


THEORIES  OF  EVOLUTION  161 

paleontology  and  other  sources — that  species  may 
also  arise  by  slow  accumulations  of  small  variations. 

One  great  value  of  his  work  is  that  it  is  based  on 
experiments  and  that  it  has  given  a  great  stimulus  to 
experimental  studies.  Experiment  was  likewise  a 
feature  of  Darwin's  work,  but  that  seems  to  have 
been  almost  overlooked  in  the  discussions  aroused  by 
his  conclusions.  De  Vries,  by  building  upon  exper- 
imental evidence,  has  led  naturalists  to  realize  that 
the  method  of  evolution  is  not  a  subject  for  argu- 
mentative discussion,  but  for  experimental  investi- 
gation. 

Other  Theories. — In  addition  to  the  four  theories 
briefly  outlined  other  theories  have  been  advanced, 
which,  in  their  relation  to  the  Darwinian  hypothesis 
of  natural  selection,  fall  into  two  categories.  There 
are  competing  theories  designed  to  replace  that  of 
natural  selection,  and  there  are  auxiliary,  or  support- 
ing theories,  that  are  designed  to  throw  new  light  on 
the  conditions  of  species-forming,  and  to  strengthen 
the  natural  selection  theory  by  its  more  complete 
elucidation.  Such  an  extensive  literature  has  grown 
up  in  the  discussion  of  these  matters,  that  even 
summaries  would  unduly  prolong  the  subject  of  this 
chapter.  The  entire  case  has  been  presented  with 


162      THE  MAIN  CURRENTS  OF  ZOOLOGY 

remarkable  clearness  in  Kellogg's  Darwinism  To-day, 
to  which  volume  the  reader  is  referred  for  fuller 
information. 

There  are,  however,  two  ideas  of  fundamental  im- 
portance in  post-Darwinian  discussions  that  should 
receive  mention.  These  are  designated  respectively, 
orthogenesis  and  isolation.  Theodor  Eimer,  since 
1888,  has  been  the  typical  representative  of  the  ideas 
of  orthogenesis — which  means  development  in  a 
straight  or  definite  direction.  He  maintains  that 
variations  of  organisms  take  place,  not  fortuitously 
in  radiating  lines,  but  follow  a  few  definite  direc- 
tions. He  insists  that  variations  are  not  preserved 
on  the  basis  of  their  utility,  but  as  the  result  of  the 
direct  inheritance  of  acquired  characters.  This  is 
intended  as  a  replacing  theory  for  that  of  natural 
selection. 

Isolation  as  a  favoring  condition  of  species- 
formation  has  been  championed  by  Moritz  Wagner 
(since  1868)  and,  more  recently,  by  David  Starr 
Jordan,  Gulick,  Romanes  and  others.  This  is  based 
on  the  obvious  fact  that  slight  variations  will  be 
more  likely  to  persist  if  the  species  in  which  they 
occur  are  segregated,  or  isolated,  so  that  those  ex- 
hibiting similar  variations  shall  be  compelled  to 


THEORIES  OF  EVOLUTION  163 

breed  together.  Slight  variations  before  they  be- 
come fixed  are  very  unstable,  and  they  would  very 
likely  disappear  if  the  breeding  were  general  with 
species  exhibiting  counter  variations.  Isolation  of 
species,  by  geographical  barriers  or  other  natural  cir- 
cumstances, would  lead  to  interbreeding  and  favor 
the  perpetuation  and  improvement  of  small  varia- 
tions. After  the  variations  are  started  and  lifted  to 
a  plane  where  natural  selection  can  take  hold,  then 
the  latter  agent  would  become  operative.  Natural 
selection  originates  nothing  but  guides  the  course  of 
evolution  after  variations  are  sufficiently  developed 
to  make  a  difference  in  the  struggle  for  existence. 

Before  closing  this  chapter  a  word  regarding  the 
present  status  of  the  doctrine  of  organic  evolution 
will  be  in  order.  With  so  many  discussions  in 
scientific  circles  regarding  aspects  of  evolution  there 
is  little  wonder  that  the  general  public  should  be 
confused,  and  that  reports  are  often  circulated  that 
there  is  a  tendency  on  the  part  of  the  scientific  world 
to  recede  from  the  doctrine  or  even,  to  surrender  it. 
This  vagueness  regarding  the  present  status  of  the 
theory  of  organic  evolution  arises  chiefly  from  not 
understanding  the  nature  of  the  points  at  issue. 
Never  before  was  the  doctrine  of  organic  evolution  so 


164     THE  MAIN  CURRENTS  OF  ZOOLOGY 

thoroughly  entrenched  in  the  mind  of  the  scientific 
world.  Never  before  was  it  so  thoroughly  supported 
by  such  a  wealth  of  compelling  evidences  which  have 
multiplied  with  the  progress  of  biological  investiga- 
tion. The  scientific  discussions  are  no  longer  re- 
garding the  occurrence  of  evolution.  The  fact  of 
evolution  is  so  widely  recognized  that  it  is  regarded 
in  the  light  of  a  great  truth  of  nature.  But,  regarding 
the  factors — the  particular  agencies  that  have  been 
at  work  in  nature  to  bring  about  this  recognized 
development  of  life — there  is  much  room  for  discus- 
sion. The  attempt  to  designate  the  particular  factor, 
or  factors,  has  given  rise  to  the  different  theories  of 
organic  evolution.  That  natural  selection  is  an 
important  agent  at  some  stages  of  the  process  is 
commonly  conceded,  but  the  factors — more  primary 
in  nature — which  produce  variation  and  adaptation 
are  more  obscure  and  will  for  a  long  time  be  subjects 
of  investigation. 


CHAPTER  XIV 

SOME    MISCELLANEOUS    TOPICS.      PAINLESS 
SURGERY,  ETC. 

No  student  of  biology  should  be  unacquainted 
with  the  circumstances  leading  up  to  the  demon- 
stration of  the  properties  of  anaesthetics  and  to 
painless  surgery.  The  discovery  of  the  methods  of 
painless  surgery  was  one  of  the  greatest  medico- 
biological  advances  of  all  time,  and  the  application  of 
these  methods  has  conferred  upon  suffering  hu- 
manity one  of  the  greatest  blessings  of  science.  It 
was  in  a  way  a  by-product  of  biological  investigation, 
and  one  of  those  advances  so  intimately  connected 
with  the  progress  of  biology  that  it  is  appropriate  to 
consider  it  within  the  scope  of  this  book. 

The  first  definite  step  that  brought  anaesthetics 
into  general  use  was  the  demonstration,  in  1846,  by 
W.  T.  G.  Morton,  that  ether  is  a  safe,  effective  and 
reliable  agent  for  producing  insensibility  to  pain 
during  a  surgical  operation. 

Since  there  were  anticipations  of  this  discovery  and 
various  claimants  to  recognition  for  the  honor  of  the 

important  achievements,  the  story  should  be  told  in 

165 


166     THE  MAIN  CURRENTS  OF  ZOOLOGY 

outline.  Although  the  general  use  of  anaesthetics  in 
surgery  dates  from  1846,  there  are  scattered  refer- 
ences in  classical  writers,  in  mediaeval  literature  and 
in  other  sources,  to  show  that  there  was  at  least 
occasional  employment  of  hemp,  of  mandrake  and 
other  opiates,  to  produce  insensibility  to  pain  during 
surgical  treatment.  Vapors  of  a  certain  kind  of 
hemp  were  used  in  ancient  times,  Mandragora  was 
used  in  the  thirteenth  century  in  Italy,  and  it  is 
recorded  that,  in  1782,  Augustus,  King  of  Poland, 
underwent  an  amputation  while  rendered  insensible 
by  a  narcotic.  But  these  occurrences  were  inciden- 
tal and  led  to  no  general  use  of  pain-dispelling  agents. 

In  1787,  Sir  Humphrey  Davy  experimented  upon 
himself  with  the  effects  of  nitrous  oxide,  commonly 
called  "laughing  gas."  His  experiments  were  in- 
teresting, and  although  he  did  not  inhale  the  gas 
to  the  point  of  complete  insensibility,  he  made  the 
suggestion  that  it  might  be  useful  in  surgical  practice. 

Again,  in  1818,  Faraday  observed  the  pain-dis- 
pelling effects  of  inhalation  of  the  vapor  of  ether, 
and  in  1822, 1833  and  1834  similar  observations  were 
reported  by  certain  American  physicians.  But  no 
practical  outcome  resulted.  These  observations  ap- 
pear "to  have  been  regarded  in  the  light  of  mere 


MISCELLANEOUS  TOPICS  167 

scientific  curiosities  and  subjects  for  lecture-room 
experiment."  Had  they  been  followed  up  by  further 
experiments  and  demonstrations  the  advent  of  pain- 
less surgery  would  have  been  much  earlier.  They 
were  vague  foreshadowings  of  this  important  event. 

The  demonstration,  the  earliest  use  and  the  com- 
munication of  the  method  of  anaesthesia,  is  an  Amer- 
ican achievement.  In  1844,  Dr.  Horace  Wells  of 
Hartford,  Connecticut,  experimented  with  nitrous 
oxide  and  began  to  use  it  for  the  painless  extraction  of 
teeth  in  his  dental  practice;  but,  owing  to  an  un- 
successful experiment  he  became  discouraged  and  did 
not  follow  the  matter  very  far.  He  also  experi- 
mented upon  himself  with  ether  but  gave  it  up  be- 
cause he  regarded  its  inhalation  as  too  disagreeable. 

Wells  communicated  his  observations  to  the 
Boston  dentist,  Dr.  W.  T.  G.  Morton,  who  acted 
upon  the  suggestion  with  great  enthusiasm  and 
energy.  Dr.  Morton  thought  that  sulphuric  ether 
was  probably  a  more  promising  agent  than  nitrous 
oxide  gas  and  experimented  with  it  extensively. 
After  experiments  on  animals,  and  on  patients  in 
his  dental  practice,  he  became  convinced  of  its 
reliability  and,  in  September  of  1846,  he  went  to  the 
Boston  surgeon,  Dr.  J.  G.  Warren,  and  requested 


168      THE  MAIN  CURRENTS  OF  ZOOLOGY 

opportunity  to  demonstrate  his  discovery  on  a 
patient  about  to  undergo  a  severe  surgical  operation 
(removal  of  a  tumor  of  the  neck)  at  the  Massachu- 
setts General  Hospital.  In  this  case,  the  results  of 
the  administration  of  ether  were  satisfactory  and  this 
new  method  of  painless  surgery  was  communicated 
to  the  medical  world.  It  was  at  first  received  with 
incredulity  but  speedily  won  recognition  both  in 
America  and  in  Europe.  Dr.  Oliver  Wendell  Holmes 
supplied  for  the  new  method  a  singularly  appro- 
priate name,  calling  it  anaesthesia,  and  the  agents 
producing  this  insensibility  to  feeling,  anaesthetics. 

The  honor  of  this  achievement  belongs  to  Dr. 
Morton  (Fig.  27),  but  other  claimants  arose.  The 
bitter  controversy  over  priority  and  credit  for  the 
discovery  was  long  drawn  out.  Dr.  Charles  T. 
Jackson,  the  chemist  of  Boston,  made  a  determined 
effort  to  secure  for  himself  credit  for  the  discovery  or, 
at  least,  equal  recognition  with  Morton.  His  ad- 
herents got  the  matter  considered  by  Congress  and  a 
committee  of  the  House  of  Representatives  voted 
him  the  credit.  More  judicious  consideration  of  his 
claims  leads  to  the  conclusion  that  his  connection 
with  the  discovery  was  incidental.  It  is  true  that  he 
experimented  with  ether,  and,  not  knowing  that 


MISCELLANEOUS  TOPICS  169 

Morton  had  already  experimented  with  it,  he  sug- 
gested to  Dr.  Morton  its  pain-expelling  effects. 
Apparently,  there  floated  in  Dr.  Jackson's  mind 
ideas  regarding  the  employment  of  ether  in  surgery, 
but  Morton  took  the  further  step  of  extensive  ex- 
periment and  use,  and,  above  all,  he  demonstrated 
in  the  Massachusetts  General  Hospital  that  it  was 
safe,  effective  and  reliable.  This  brought  it  into 
general  use. 

Another  man,  Dr.  Crawford  Long,  nearly  antic- 
ipated the  discovery  of  Morton.  He  was  a  practi- 
tioner in  a  small  town  of  Georgia,  and  in  March, 
1842,  he  had  placed  a  patient  profoundly  under  the 
influence  of  ether  and  had  painlessly  removed  a 
tumor  from  the  neck.  He  had  also  used  ether  in 
other  operations  prior  to  1846.  In  point  of  tune  he 
antedated  Morton,  but  he  had  some  misgivings  as  to 
whether  it  was  the  effect  of  the  ether  that  produced 
insensibility,  or  a  sort  of  hypnotic  influence  exerted 
by  himself,  and  his  results  were  not  published  till 
1849. 

Although  Jackson  had  vaguely  divined  the  possi- 
ble utility  of  ether  in  surgery,  and  Long  had  used  it 
in  local  country  practice,  it  remained  for  Morton  to 
carry  the  matter  to  a  practical  conclusion.  It  re- 


i  yo     THE  MAIN  CURRENTS  OF  ZOOLOGY 

mained  for  him,  on  the  basis  of  his  own  experiments, 
followed  by  a  hospital  demonstration,  to  introduce 
the  method  of  anaesthesia  to  the  medical  world. 
Morton's  work  was  on  a  different  plane  from  that  of 
his  predecessors.  Except  for  its  practical  use  by 
Long  the  work  of  others  was  merely  anticipatory 
glimpses,  and  Morton,  by  demonstrating  the  safety 
and  reliability  of  ether  as  an  anaesthetic  agent,  in- 
troduced the  method  into  surgery. 

The  new  method  was  put  into  immediate  use.  In 
1847,  after  ether  had  been  successfully  used  in 
Europe,  the  Scottish  surgeon,  Sir  James  Simpson, 
introduced  the  use  of  chloroform  which  had  been 
previously  used  in  France  by  Flourens  in  experimen- 
tation on  animals.  Since  that  time  the  methods  of 
administering  ether  and  chloroform  have  been 
greatly  improved  and  they  remain  to-day  the  chief 
agents  used  in  anaesthesia. 

Vaccination — Edward  Jenner. — The  method  of 
vaccination  for  small-pox  was  an  original  and  unique 
discovery,  and  antedated  by  more  than  three-fourths 
of  a  century,  the  modern  vaccinations  and  serum 
inoculations  devised  by  Pasteur. 

Formerly,  small-pox  was  a  dreaded  and  highly 
contagious  disease.  It  was  very  prevalent,  sweeping 


MISCELLANEOUS  TOPICS  171 

as  an  epidemic  over  communities  and  carrying  terror 
and  death  in  its  path.  Edward  Jenner  came  from  a 
dairy  county — Gloucestershire — of  England  where 
a  belief  existed  among  the  dairy  people  that  persons 
who  had  contracted  cow-pox  were  immune  from 
small-pox.  Cows  are  sometimes  affected  with  a  kind 
of  disease  accompanied  by  watery  pustules  on  the 
udders,  the  hands  of  milkers  become  infected  from 
these,  and,  after  a  mild  sickness,  those  individuals 
were  no  longer  susceptible  to  small-pox.  It  was  the 
quality  of  sagacity  in  Jenner  that  led  him  to  make 
use  of  this  wide-spread  belief  and  to  investigate  it 
with  the  trained  mind  and  the  powers  of  a  scientific 
education.  His  discovery  was  a  triumph  of  experi- 
mental science. 

Edward  Jenner,  the  discoverer  (1749-1823)  (Fig. 
28)  went  to  London  at  the  age  of  twenty-one,  in 
1770,  to  pursue  medical  studies  and  came  under  the 
tutelage  of  the  famous  Dr.  John  Hunter.  He  was 
broadened  by  his  contact  with  Hunter  and  by 
studies  of  comparative  anatomy  in  his  extensive 
museum.  He  attempted  to  interest  Hunter  in  the 
question  of  immunity  from  small-pox,  but  Hunter, 
his  preceptor,  was  too  busily  engaged  with  other 
matters  to  give  it  serious  attention.  Accordingly, 


172     THE  MAIN  CURRENTS  OF  ZOOLOGY 

Jenner  went  to  work  on  his  own  account  to  investi- 
gate the  basis  of  the  belief  of  the  dairy  people  of  his 
native  county. 

After  some  experimentation  he  devised  means  of 
vaccinating  people  with  the  relatively  harmless  virus 
of  cow-pox.  In  1796,  he  made  inoculations  with 
cow-pox  material  and  after  the  recovery  of  his 
patients  from  a  mild  sickness,  in  two  months,  he 
inoculated  the  same  individuals  with  small-pox 
matter  but  they  remained  unaffected.  This  con- 
vinced Jenner  that  this  method  was  a  protection 
against  the  contagion  of  small-pox,  and  two  years 
after,  in  1798,  he  announced  his  discovery  to  the 
world. 

It  was  immediately  put  into  use  and  Jenner  was 
heralded  as  a  great  benefactor.  Even  before  Jenner 
the  voluntary  inoculation  with  the  virus  of  small-pox 
had  been  advocated.  The  disease  was  so  prevalent 
and  the  chance  to  escape  the  contagion  was  so  small 
that  some  were  willing  to  run  the  risk  of  a  voluntary 
inoculation,  under  the  belief  that  these  inoculations 
resulted  in  mild  cases,  but  these  were  sometimes 
fatal. 

Jenner,  however,  investigated  the  matter  with 
scientific  methods  and  devised  a  method  of  procuring 


MISCELLANEOUS  TOPICS  173 

and  using  the  virus  of  cow-pox  so  as  to  secure  pro- 
tection against  the  contagion  of  this  most  dreaded 
disease.  At  the  present  time  the  use  of  his  method  is 
so  general — being  at  times  prescribed  by  law — that 
small-pox,  from  being  one  of  the  most  common 
diseases,  is  now  comparatively  rare. 

The  objections  raised  to  vaccination  are  usually 
based  on  the  fear  of  communicating  other  serious 
conditions.  But  this  danger  is  reduced  to  a  min- 
imum by  the  production  of  pure  and  standard  cul- 
tures. 


CHAPTER  XV 

THE  TEN  FOREMOST  MEN  OF  ZOOLOGICAL 
HISTORY.  THE  RANK  OF  DIFFERENT  NA- 
TIONS IN  BIOLOGICAL  PROGRESS 

IT  is  a  popular  pastime  to  make  out  lists  of  the 
foremost  men  in  different  lines  of  human  achieve- 
ment. In  any  subject  it  is  natural  to  wish  to  settle 
the  question,  Who  were  the  great  path-breakers? 
It  is  a  hazardous  undertaking  to  attempt  to  designate 
any  particular  number,  and  it  would  be  wrong  to 
pretend,  that  there  is  an  absolute  standard  upon 
which  the  ten  men  of  greatest  distinction  can  be 
selected.  The  formulation  of  such  a  tentative 
group,  for  zoology,  if  not  taken  too  seriously,  will 
serve  some  useful  purpose.  It  will  stimulate  thought 
and  direct  attention  to  some  of  the  most  eminent  men 
and  to  their  contributions  to  zoological  progress. 
The  point  of  view  adopted  will  lead  to  divergent 
results.  Shall  the  foremost  men  be  selected  from  the 
standpoint  of  wide  influence,  or  from  that  of  intel- 
lectual superiority  of  the  individual  and  the  quality 
of  his  work?  The  former  basis  would  give  a  different 

group  from  the  latter. 

174 


THE  TEN  FOREMOST  MEN  175 

The  list  of  ten  men  given  below  is  based  on  the 
influence  exerted  by  certain  advances  with  which 
they  were  prominently  connected,  rather  than  merely 
on  the  high  quality  of  their  individual  output  as 
scientific  investigators.  In  some  cases  the  highest 
intellectual  rank  and  the  most  eminent  researches  are 
combined  in  one  individual  of  wide  influence,  in 
other  instances,  the  influence  of  certain  happy  dis- 
coveries (as  in  the  case  of  Mendel)  are  out  of  pro- 
portion to  the  relative  rank  of  the  man  as  a  bi- 
ologist. 

1.  Harvey. — Passing  over  Aristotle,  who  undoubt- 
edly was  the  greatest  scientific  investigator  of  an- 
tiquity, and  beginning  with  the  revival  of  science  in 
the  sixteenth  century,  it  seems  to  the  writer  that 
the  pioneer  work  of  Wm.  Harvey  (1578-1657)  re- 
quires first  recognition.  He  was  at  once  observer  and 
experimenter.  The  influence  of  his  work  on  the 
circulation  of  the  blood  was  profound  and  construc- 
tive. It  not  only  gave  for  the  first  time  a  rational 
basis  for  the  progress  of  physiology  but  also  provided 
biological  science  with  a  new  method  and  stimulated 
investigation.  His  book  on  the  movement  of  the 
heart  and  the  blood  (De  Motu  Cordis  et  Sanguinis) 
published  in  1628,  is  a  biological  classic.  He  also 


1 76      THE  MAIN  CURRENTS  OF  ZOOLOGY 

made  the  first  (after  the  Renaissance)  independent 
advance  in  embryology  (1651)  and  exercised  consid- 
erable influence  on  the  progress  of  morphology. 

Although  Vesalius  (1514-1564)  before  Harvey  had 
established  the  method  of  independent  observa- 
tion (human  anatomy,  1543)  he  is  subordinate  to 
Harvey. 

2.  Malpighi. — Our  second  selection  in  chron- 
ological order  is  Malpighi  (1628-1694).  A  careful 
observer,  making  progress  in  Minute  Anatomy  of 
animals,  as  in  his  famous  monograph  on  the  anatomy 
of  the  silkworm  (1670),  in  the  anatomy  of  plants 
(1671  and  1675),  and,  especially,  in  embryology 
(1672).  He  was  the  first  also  (in  1661)  to  see  the  ac- 
tual circulation  of  blood  in  the  capillaries.  Through 
the  exactness  and  the  range  of  his  observations,  his 
spirit  and  his  teaching  of  anatomy,  he  was  directly 
connected  with  future  progress. 

Two  of  his  contemporaries  should  be  mentioned — 
Leeuwenhoek  and  Swammerdam.  Leeuwenhoek 
was  more  discursive  and  less  directly  connected  with 
progress.  Swammerdam  was  more  exact  in  his 
studies  of  insect  anatomy,  but  the  range  of  his  work 
was  more  limited  and  the  publication  of  his  complete 
investigations  was  delayed  till  1738.  (During  his 


THE  TEN  FOREMOST  MEN  177 

lifetime,  a  small  volume  on  the  general  history  of 
insects  was  published,  in  1669.) 

3.  Linnaeus. — From  the  standpoint  of  wide  in- 
fluence Linnaeus  (1707-1778)  should  be  included  in 
our  list.    He  was  the  man  who  brought  the  present 
method  of  naming  animals  and  plants  into  use  and 
thereby  gave  to  natural  history  a  new  language.    He 
also  introduced  greater  precision  in  the  whole  field  of 
description  and  classification.     The  stimulus  im- 
parted to  natural  history  by  the  work  of  Linnaeus  was 
immense.     Collection  and  classification  of  animals 
and  plants  was  carried  on  with  enthusiasm  and  the 
knowledge  of  the  animals  of  the  globe  rapidly  ex- 
tended.   Linnaeus  also  directed  attention  to  species, 
and  thereby  served  to  lay  the  foundation  for  the 
question  of  the  Origin  of  Species,  which  had  such 
important  connection  in  the  work  of  Lamarck  and 
Darwin. 

4.  Cuvier. — In  the  early  years  of  the  nineteenth 
century  this  French  legislator  and  zoologist  gave 
a  new  direction  to  zoological  study.    While  Linnaeus 
had  given  a  great  impulse  to  natural  history  and  to 
the  study  of  the  organism  as  a  whole,  Cuvier  (1769- 
1832)    started  a   strong  movement  for  structural 
zoology.    By  extensive  dissections  he  centered  atten- 


1 78      THE  MAIN  CURRENTS  OF  ZOOLOGY 

tion  on  the  structure  of  animals  and  founded  com- 
parative anatomy.  He  also  laid  foundations  of  the 
science  of  Vertebrate  Paleontology.  On  the  whole, 
his  influence  on  the  progress  of  zoology  was  so  exten- 
sive that  he  is  to  be  heralded  as  one  of  the  great  path- 
breakers. 

5.  Von  Baer. — One  of  the  great  intellects  of  the 
nineteenth  century,  von  Baer  (1792-1876),  is  to  be 
remembered  for  the  great  service  of  founding  in 
1828  embryology  on  modern  lines.    This  has  proved 
to  be  one  of  the  most  helpful  and  illuminating  lines 
of  zoological  investigation.      This  supplemented  the 
work  of  Cuvier  and  from  the  two  combined,  compara- 
tive anatomy  and  embryology  of  animals,  for  many 
years  proceeded  the  best  results  of  zoological  study. 

6.  Johannes   Miiller. — Johannes    Muller    (1801- 
1858)  made  physiology  comparative,  and  stimulated 
researches   in   both   physiology    and   morphology. 
Through    his    superb    talents    and    extraordinary 
qualities  as  a  leader  he  helped  in  a  signal  way  to 
advance  the  standards  of  zoological  investigation. 
By  appointment  a  professor  of  physiology,  he  was 
also  an  investigator  in  zoological  lines  (morphology) 
and  promoted  exactness  of  observation  and  high 
quality  of  work.     Considered  strictly  as  a  phys- 


THE  TEN  FOREMOST  MEN  179 

iologist  his  contributions  were  less  eminent  than  those 
of  Claude  Bernard,  but  with  a  larger  number  of 
disciples  and  with  unusual  gift  for  stimulating  and 
inspiring  his  students,  he  exerted  a  broad  influence 
for  progress. 

7.  Pasteur. — From  all  points  of  view  there  can 
be  no  doubt  of  the  rank  of  Pasteur  (1822-1895)  as 
one  of  the  greatest  biologists  of  the  nineteenth  cen- 
tury.   He  is  placed  here  as  one  of  the  men  of  greatest 
influence  on  the  progress  of  zoology  because  zoology 
is  the  central  subject  of  biology.    There  is  continued 
growth  in  the  sum  total  of  his  influence.    In  close 
relation  with  the  influence  of  Pasteur  should  be  men- 
tioned the  names  of  Koch  and  Lister. 

8.  Darwin. — Another,  whose  place  is  unquestioned 
hi  the  rank  of  the  foremost  men  of  zoology,  is 
Charles  Darwin  (1809-1882).    His  theory  of  natural 
selection  as  an  agent  of  organic  evolution  has  had  the 
most  stimulating  effect  upon  zoological  progress  of 
any  scientific  advance.     Although  his  predecessor, 
Lamarck,  is  accorded  high  place  at  the  present  day, 
no  other  man  connected  with  the  idea  of  organic 
evolution  has  exerted  the  wide  influence  of  Charles 
Darwin. 

9.  Max   Schultze. — This   investigator    embraced 


i8o     THE  MAIN  CURRENTS  OF  ZOOLOGY 

in  his  work  the  summation  of  the  protoplasm  idea 
and  the  reform  of  the  cell-theory.  The  effect  of 
these  two  conceptions  on  zoology  cannot  be  over- 
estimated. Taking  rank  with  the  greatest  dis- 
coveries of  the  nineteenth  century,  their  direct 
application  in  zoology  have  been  of  supreme  Value. 
Schultze  (1825-1874)  also  founded  one  of  the  most 
influencial  periodicals  of  zoological  science,  the 
Archiv  fur  Mikroscopische  Anatomie. 

10.  Mendel. — Since  1900,  the  date  of  the  redis- 
covery of  alternative  inheritance  and  purity  of  the 
germinal  elements,  Mendelian  inheritance  has  been 
one  of  the  most  actively  pursued  of  biological  topics. 
Mendel  (1822-1884)  made  his  chief  observations  on 
plants  and  published  the  same  in  1866-1867,  but, 
the  study  of  Mendelian  inheritance  in  animal  forms 
has  exerted  such  a  great  influence,  that  his  name  is 
properly  embraced  in  this  list.  On  the  basis  of 
strictly  scientific  output  and  commanding  intel- 
lectuality there  are  other  names  that  would  contest 
the  position  with  Mendel,  but,  on  the  basis  of  the 
wide  influence  of  his  happy  discoveries,  he  is  entitled 
to  rank  with  the  men  whose  work  has  stimulated 
zoological  investigations  and  been  of  the  widest 
influence. 


RANK  OF  DIFFERENT  NATIONS          181 

Rank  of  the  Nations  in  Biological  (Zoological) 
Progress. — The  relative  position  of  the  different 
nationalities  in  biological  progress  from  the  zoological 
side  is  a  question  that  offers  ground  for  conflicting 
opinions.  It  is  nevertheless  of  very  great  interest  to 
students  of  zoology  and  is  an  appropriate  matter  for 
consideration  in  this  connection.  The  general  con- 
clusion appears  to  me  justified  that  no  nation  takes 
absolute  preeminence  in  originality  and  in  quality  of 
investigation.  Notwithstanding  the  brilliancy  of  the 
French,  the  deep  philosophical  contributions  of  the 
English,  and  the  monumental  industry  of  the  Ger- 
mans, not  one  of  these  nations  can  justly  claim  a 
position  of  undisputed  supremacy. 

The  fact  should  not  be  overlooked  that  there  have 
been  notable  pieces  of  zoological  work  from  Italy, 
from  Ramon  y  Cajal  in  Spain,  from  Russia  and  from 
the  United  States,  but  for  the  present  inquiry,  the 
matter  is  chiefly  conned  to  the  highly  developed 
nations  of  Europe,  the  English,  the  French,  and  the 
Germans. 

Let  us  first  examine  the  part  played  by  these  three 
nations  as  path-breakers  in  the  five  outstanding 
biological  advances  of  the  nineteenth  century. 

The  advance  of  greatest  importance,  the  theory  of 


1 82     THE  MAIN  CURRENTS  OF  ZOOLOGY 

organic  evolution,  is  to  be  credited  in  its  inception  to 
the  French  (Lamarck)  and  the  English  (Charles 
Darwin) .  This  is  probably  the  greatest  philosophical 
contribution  of  the  nineteenth  century.  After  it  was 
well  under  way  it  was  taken  up  by  scholars  of  differ- 
ent nationalities.  Weismann,  the  German,  De  Vries, 
the  Hollander,  have  made  notable  contributions,  and, 
in  America,  Cope  and  others  brought  forward  new 
aspects  of  Lamarckism  and  established  the  school  of 
Neo-Lamarckism. 

To  the  genius  of  Pasteur  more  than  to  any  other 
worker  we  owe  the  basis  of  the  germ-theory  of 
disease  with  its  concomitants  as  antitoxins,  serum 
injections  and  vaccines.  The  Englishman,  Lister, 
applied  these  to  surgery  and  the  German,  Robert 
Koch,  (a  student  of  Ferdinand  Cohn),  established 
bacteriology  (to  which  these  matters  belong)  as  an 
independent  science. 

The  discovery  of  protoplasm  is  credited  to  the 
Frenchman  Dujardin,  but  the  great  elaboration  of 
the  idea  to  Max  Schultze,  the  German. 

The  cell-theory  is  a  product  of  German  scholar- 
ship— Schleiden  and  Schwann  being  founders  and 
Schultze  developer  of  this  important  conception. 

In  the  experimental  study  of  heredity,  while  the 


RANK  OF  DIFFERENT  NATIONS          183 

work  of  Francis  Galton,  the  Englishman,  was  of  high 
quality  and  received  earlier  notice,  it  was  over- 
shadowed by  the  importance  of  MendeFs  (Austrian) 
results. 

The  encouragement  of  research  in  the  German 
universities — making  results  of  investigations  the 
basis  of  recognition  and  advancement  in  scholarly 
occupations — has  had  tremendous  influence.  The 
degrees  conferred  by  German  universities  require  the 
publication  of  a  piece  of  research  as  a  thesis,  and  if 
merely  volume  of  output  is  considered,  the  Germans 
have  been  leaders — but  for  originality,  quality  and 
philosophical  insight  the  French  and  the  English  take 
higher  rank. 

Turning  from  the  outstanding  advances  we  shall 
consider  who  have  been  path-breakers  in  some  of  the 
different  divisions  of  zoological  science — omitting  the 
mention  of  the  living  and  most  recent  personalities. 

In  Physiology,  if  the  Germans  have  their  Haller 
and  Johannes  Muller,  so  the  English  have  their 
William  Harvey  and  Burdon-Sanderson  and  the 
French  their  Magendie  and  Claude  Bernard.  The 
latter  occupies  a  unique  position.  He  was  the 
veritable  law-giver  of  experimental  physiology.  As 
an  investigator  probably  he  was  as  Howell  has  said, 


1 84     THE  MAIN  CURRENTS  OF  ZOOLOGY 

"the  greatest  physiologist  of  all  time."  He  is  per- 
haps better  compared  with  Ludwig  than  with 
Johannes  Muller. 

In  Embryology  while  the  Germans  have  Von  Baer 
(Russian)  as  founder,  the  Italians  have  Malpighi,  as 
forerunner,  and  the  English  have  Francis  M.  Balfour, 
as  developer. 

In  Comparative  Anatomy  the  French  have  Cuvier, 
H.  Milne-Edwards  and  Lacaze-Duthiers,  the  Eng- 
lish, John  Hunter,  Richard  Owen  and  Huxley  to  off- 
set Meckel,  Muller  and  Karl  Gegenbaur. 

The  scientific  output  of  a  nation  especially  as  to 
quality,  is  largely  an  expression  of  national  tempera- 
ment. 

The  French  are  remarkable  for  lucidity,  for  in- 
dsiveness,  they  are  subtle  and  accurate  in  analysis 
and  exhibit  great  originality. 

In  zoology,  the  English  are  notable  for  philosoph- 
ical grasp  (Darwin)  and  have  a  passion  for  intel- 
lectual honesty  (Huxley). 

The  German  mentality  is  more  ponderous,  less 
original,  but  has  been  guided  by  great  industry, 
finding  suggestions  in  the  work  of  investigations  of 
other  nations  and  elaborating  these  suggestions  with 
diligence  and  thoroughness.  If  other  nations  have 


RANK  OF  DIFFERENT  NATIONS          185 

shown  greater  originality,  and  greater  philosophical 
grasp  in  zoological  fields,  the  Germans  have  been 
better  developers  of  these  new  territories. 

If  we  select  the  overshadowing  contributions  of 
Darwin  and  Pasteur  we  might  be  inclined  to  place 
English  and  French  contributions  to  biological 
thought  above  those  of  the  Germans.  This  is,  how- 
ever, a  too  restricted  view,  and,  broadly  considered, 
it  appears  that  the  different  nations  break  about 
even  as  regards  eminent  contributions  to  biological 
progress.  They  constitute  an  international  group  of 
peers  among  whom  it  is  invidious  to  make  distinc- 
tions. 

The  fact  that  German  contributions  to  scholarship 
have  been  more  energetically  advertised  and  are 
therefore  more  widely  known,  has  given  rise  to  a 
wide-spread  opinion  that  the  Germans  have  been 
unquestioned  leaders  hi  biological  progress.  But, 
this  general  impression  gives  way  under  a  candid 
consideration  of  the  quality  and  the  importance  of 
the  scholarly  output  of  other  nations. 

Zoology  and  Intellectual  Progress. — Undoubtedly 
the  progress  of  zoology  has  played  an  important 
part  in  the  intellectual  development  of  civilized 
mankind,  but  the  reason  for  this  is  only  vaguely 


1 86      THE  MAIN  CURRENTS  OF  ZOOLOGY 

understood.  That  the  progress  of  science,  broadly 
speaking,  has  been  beneficial  will  not  be  disputed. 
Manifestly  it  has  been  a  powerful  reconstructing 
force.  Wherever  investigations  of  the  phenomena  of 
nature  have  taken  away  old  beliefs  they  have  sub- 
stituted something  better  and  more  consistent.  But 
zoology  in  particular,  in  the  last  half  century,  has 
concerned  itself  with  the  investigation  of  the  phe- 
nomena of  all  living  animals  of  the  globe.  This  has 
brought  zoological  investigation  into  a  realm  that 
touches  more  closely  than  any  other,  the  problems 
of  human  origin  and  destiny. 

The  phenomena  of  life  are  so  difficult  of  analysis 
and  apparently  so  mysterious  that,  naturally,  there 
was  a  great  amount  of  metaphysical  speculation  re- 
garding their  interpretation,  and  many  superstitions 
and  misconceptions  arose.  Zoology  undertook  to 
investigate  these  problems  and  came  into  conflict 
with  traditional  opinion.  The  atmosphere  of  thought 
engendered  by  the  progress  of  these  studies  of  animal 
life  was  broadening,  and  in  its  influence  as  wholesome 
as  it  was  stimulating.  Wherever  biological  investiga- 
tion prospered  the  results  shed  light  and  dispelled 
error.  There  was  progress -in  straight  thinking. 

Immediately   after   the   Renaissance   these   new 


RANK  OF  DIFFERENT  NATIONS          187 

ideas  began  expanding  the  horizon  of  thought  and 
provoked  many  controversies,  which  for  the  time 
were  often  bitter,  but,  in  many  instances,  resulted 
in  freeing  the  mind  from  the  bonds  of  inherited  and 
traditional  superstitions. 

Gradually  all  animal  life  came  to  be  looked  on  as 
the  result  of  an  orderly  progress  with  no  place  for 
the  idea  of  chance.  The  idea  of  the  constancy  of 
nature  was  established.  Then  arrived,  in  the  last 
half  of  the  nineteenth  century,  largely  as  the  result 
of  zoological  progress,  the  doctrine  of  organic 
evolution  which  produced  a  mental  revolution.  It  is 
generally  recognized  that  from  the  time  of  the  re- 
vival of  scientific  learning  to  the  present,  while  all 
scientific  study  was  making  towards  enlightenment, 
still,  the  investigation  of  problems  involving  animal 
life  had  unusually  broad  influence  in  promoting 
intellectual  progress. 

The  controversies  engendered  were  often  against 
theological  opinion,  but  these  flashes  of  enlighten- 
ment were  by  no  means  confined  to  that  territory. 
Scientific  dogma  (as  that  of  the  fixity  of  species)  and 
medical  tradition  (as  to  the  source  and  the  nature 
of  disease)  also  gave  way  to  investigations  of  a 
biological  character. 


CHAPTER  XVI 
SOME  USEFUL  BOOKS 

THE  books  and  periodical  articles  in  the  field  of 
zoology  are  so  numerous  and  cover  such  a  wide 
range  of  topics  that  some  sort  of  guide  to  the  best 
reading  is  nearly  indispensable. 

A  continually  increasing  number  of  persons  take 
an  interest  in  the  larger  ideas  that  have  developed 
from  the  critical  investigation  of  animals,  and  this 
class  of  readers  often  seek  for  palatable  and  satis- 
fying literature  on  zoological  subjects. 

The  writings  appeal  to  various  kinds  of  interest — 
there  are  the  more  popular  and  the  more  technical. 
In  selecting  reading  we  must  recognize  that  refer- 
ences which  are  good  for  one  purpose  often  are  not 
good  for  another.  Moreover,  the  focus  of  interest  of 
the  reader  varies  with  his  mood  as  well  as  with  his 
purpose,  and  the  selection  of  suitable  reading  for 
different  needs  is  a  matter  of  no  little  difficulty. 

There  are  informing  books  about  insects,  birds  and 
protozoa,  but  these  will  not  be  specifically  adapted 
to  one  whose  chief  interests  are  in  evolution  or 
genetics. 

188 


SOME  USEFUL  BOOKS  189 

The  more  technical  publications  are  standardized 
and  are  less  difficult  to  indicate  than  good  sources  of  a 
popular  character.  For  one  whose  interest  in  the 
results  of  zoological  studies  is  beginning  to  grow, 
it  is  a  great  assistance  to  have  some  references  to 
reliable  and  trustworthy  literature  for  fire-side 
reading,  in  addition  to  the  books  of  general  reference 
which  will  be  consulted  only  at  intervals. 

There  are  books  that  supply  stimulus  and  promote 
a  feeling  for  the  work  of  the  naturalist,  such  as  Dar- 
win's Voyage  of  the  Beagle,  Bates's  A  Naturalist  on 
The  River  Amazon,  Wallace's  Malay  Archipelago  and 
those  writings  that  bring  us  into  contact  with  great 
personalities  such  as  the  biographies  of  Darwin, 
Pasteur,  Huxley  and  Lister. 

In  the  references  indicated  below  attention  has 
been  given  to  selecting  sources  of  unquestioned  merit 
and  reliability,  but  no  claim  is  made  to  giving  a 
balanced  list  of  reading.  Assuming  that  a  more 
general  interest  exists  in  historical  phases  and  in 
biographies,  I  have  cited  a  relatively  larger  number 
of  references  of  that  nature. 

The  object  of  the  reading  lists  is  to  supply — not  in 
too  great  number — reliable  and  trustworthy  refer- 
ences to  a  variety  of  zoological  subjects.  The  more 


190     THE  MAIN  CURRENTS  OF  ZOOLOGY 

advanced  student  who  has  need  of  zoological  refer- 
ences on  subjects  not  included  will  know  how  to  go 
about  finding  them.  The  general  reader  will  also 
find  additional  biographical  sketches  as  well  as 
general  topics  referred  to  in  the  indices  of  the  period- 
ical literature  with  which  nearly  all  libraries  are 
provided. 

It  has  seemed  desirable  to  give,  first,  a  suggested 
list  of  fifty  books  for  the  nucleus  of  a  reference  li- 
brary, and  to  follow  this  list  with  additional  titles  of 
books  and  articles  in  which  the  reader  may  find  food 
for  various  kinds  of  internal  hunger  which  he  may 
feel  from  time  to  time  for  supplementary  reading. 


READING  LISTS  OF  BOOKS  AND  PERIODICAL 
ARTICLES  ON  ZOOLOGICAL  SUBJECTS 

(A)  A  REFERENCE  LIBRARY  OF  FIFTY  BOOKS 

A  suggested  reference  library  of  fifty  titles  including,  be- 
sides manuals  and  text-books,  books  on  special  topics  of 
zoological  science.  Among  these  special  topics  are  biog- 
raphies, historical  phases,  evolution,  genetics,  heredity, 
cytology,  ecology,  birds,  insects,  protozoa,  etc.  The  books 
are  arranged  according  to  topics  and  not  in  the  order  of 
preference. 

HERTWIG,  RICHARD.  A  Manual  of  Zoology,  translated  and 
edited  by  J.  S.  Kingsley,  1902.  Revised  edition,  1912. 
This  is  a  standard  reference,  or  PARKER  and  HASWELL'S 
Text-Book  of  Zoology,  2  vols.,  2nd  edition,  1910,  or 
THOMSON'S  Outlines  of  Zoology,  3rd  edition,  1899. 

WIEDERSHEIM,  ROBERT.  Comparative  Anatomy  of  Verte- 
brates, translated  by  W.  N.  Parker,  3rd  edition,  1907. 

MORGAN,  THOMAS  H.    Experimental  Zoology,  1907. 

DARWIN,  CHARLES  R.  A  Naturalist's  Voyage  Round  the 
World.  New  edition,  1880.  Also  published  under  the 
title  The  Voyage  of  the  Beagle. 

DARWIN,  CHARLES  R.  The  Origin  of  Species,  1859.  Many 
subsequent  editions. 

PACKARD,  A.  S.  Lamarck,  The  Founder  of  Evolution,  His 
Life  and  Work,  1901. 

WEISMANN,  AUGUST.  The  Evolution  Theory  translated  by 
J.  A.  and  Margaret  Thomson,  2  vols.,  1904. 

DE  VRIES,  HUGO.  Species  and  Varieties,  their  Origin  by 
Mutation,  1905. 

191 


192     THE  MAIN  CURRENTS  OF  ZOOLOGY 

ROMANES,  GEORGE  J.  Darwin  and  After  Darwin,  Vol.  I, 
1895.  Or  WALLACE,  ALFRED  R.,  Darwinism,  1889. 

KELLOGG,  VERNON  L,    Darwinism  To-day,  1907. 

JUDD,  JOHN  W.    The  Coming  of  Evolution,  1910. 

JORDAN,  DAVID  S.,  and  KELLOGG,  VERNON.  Evolution  and 
Animal  Life,  1907. 

LULL,  R.  S.    Organic  Evolution,  1917. 

HUXLEY,  T.  H.  Man's  Place  in  Nature,  in  his  Collected 
Essays,  1900.  Also  published  in  many  forms. 

OSBORN,  HENRY  F.    Men  of  the  Old  Stone  Age,  1916. 

FOSTER,  MICHAEL.  Lectures  on  the  History  of  Physiology 
During  the  i6th,  i?th,  and  i8th  Centuries,  1901. 

THOMSON,  J.  ARTHUR.  The  Science  of  Life,  An  Outline  of 
the  History  of  Biology  and  Its  Recent  Advances,  1899. 

LOCY,  WILLIAM  A.  Biology  and  Its  Makers,  3rd  edition, 
1915.  Historical  phases. 

DARWIN,  F.    Life  and  Letters  of  Charles  Darwin,  2  vols.,  1887. 

HUXLEY,  LEONARD.  Life  and  Letters  of  Thomas  Henry  Hux- 
ley, 2  vols.,  1901. 

FRANKLAND,  PERCY  and  G.    Pasteur,  1901. 

PAGET,  STEPHEN.    Pasteur  and  After  Pasteur,  1914. 

WRENCH,  G.  T.    Lord  Lister,  His  Life  and  Work,  1913. 

KELLY,  HOWARD  A.    Walter  Reed  and  Yellow  Fever,  1906. 

SEDGWICK,  WILLIAM  T.,  and  WILSON,  EDMUND  B.  General 
Biology,  revised  edition,  1895. 

DARWIN,  CHARLES.  Formation  of  Vegetable  Mould  through 
the  action  of  Worms,  1881. 

WILSON,  EDMUND  B.  The  Cell  in  Development  and  Inheri- 
tance, 1896. 

WALTER,  H.  E.    Genetics,  1913. 

CONKLIN,  E.  G.  Heredity  and  Environment  in  the  Develop- 
ment of  Men,  1915. 

DAVENPORT,  CHAS.  B.   Heredity  in  Relation  to  Eugenics,  191 1. 


BIBLIOGRAPHY  193 

BATESON,  W.  Mendel's  Principles  of  Heredity,  with  transla- 
tions of  his  original  papers  on  hybridization,  1902. 

PUNNETT,  R.  C.    Mendelism,  1911. 

SHELFORD,  VICTOR  E.  Animal  Communities  in  Temperate 
America,  1913. 

CHAPMAN,  FRANK  M.    Bird-Life,  1899. 

BARROWS,  WALTER  B.  Michigan  Bird  Life,  Lansing,  Michi- 
gan, 1912. 

COMSTOCK,  JOHN  H.,  and  BOTSFORD,  ANNA.  A  Manual  for 
the  Study  of  Insects,  2nd  Edition,  1899. 

HOLLAND,  W.  J.    The  Butterfly  Book,  1898. 

FABRE,  J.  H.    The  Hunting  Wasps,  1913. 

HUXLEY,  T.  H.  The  Crayfish — An  Introduction  to  Zoology, 
1881,  also  1906. 

BAILY,  F.  R.,  and  MILLER,  A.  M.  Text-Book  of  Embryology, 
3rd  edition,  1916. 

LILLIE,  F.  R.    The  Development  of  the  Chick,  1908. 

CALKINS,  G.  N.  The  Protozoa,  1901.  Also,  Protozoology, 
1909. 

JORDAN,  DAVID  S.  A  Manual  of  Vertebrates,  new  edition, 
1916. 

PRATT,  HENRY  S.  A  Manual  of  Common  Invertebrate  Ani- 
mals— exclusive  of  insects,  1916. 

HUXLEY,  T.  H.  Lessons  in  Elementary  Physiology,  edited 
and  revised  by  Joseph  Bancroft,  1915,  or  MARTIN,  H.  N., 
The  Human  Body,  new  edition,  1917. 

HERRICK,  C.  J.   An  Introduction  to  Neurology,  1916. 

VERWORN,  MAX.  General  Physiology,  translated  by  Fred- 
erick S.  Lee,  1899. 

THOMSON,  J.  ARTHUR.    The  Study  of  Animal  Life,  1892. 

MARSHALL,  J.  MILNES.  The  Frog,  new  edition,  1916,  or 
HOLMES,  Biology  of  the  Frog,  1906. 

BEDDARD,  P.  E.    A  Text-Book  of  Zoogeography,  1895. 


194     THE  MAIN  CURRENTS  OF  ZOOLOGY 


(B)  SUPPLEMENTARY    LISTS    OF    BOOKS    AND 
PERIODICAL  ARTICLES 

Embracing:  (i)  History  and  Biography;  (2)  Manuals  and 
Text-Books  on  Zoology;  (3)  Comparative  Anatomy,  Em- 
bryology, etc.;  (4)  Books  on  special  topics  and  (5)  Mis- 
cellaneous. 

(i)  HISTORY  AND  BIOGRAPHY 
(a)  History 

CARUS,  VICTOR.  Geschichte  der  Zoologie,  1872.  Also  Histoire 
de  la  Zoologie,  1880.  A  work  of  scholarship. 

CUVIER,  GEORGES.  Histoire  des  Sciences  Naturelles,  5  vols., 
1841-1845.  Excellent.  Written  from  an  examination 
of  the  original  documents. 

FOSTER,  MICHAEL.  Lectures  on  the  History  of  Physiology, 
1901.  Fascinatingly  written.  Notable  for  poise  and 
judicial  estimates,  based  on  the  use  of  the  original 
documents. 

GEDDES,  P.  "  A  Synthetic  Outline  of  the  History  of  Biology." 
Proc.  Roy.  Soc.  Edinb.,  1885-1886. 

HERTWIG,  OSKAR.  "The  Growth  of  Biology  in  the  Nine- 
teenth Century."  Ann.  Rept.  Smithson.  Inst.,  1900. 

LANKESTER,  E.  RAY.  "  The  History  and  Scope  of  Zoology," 
in  The  Advancement  of  Science,  1890.  Same  article  in 
the  Ency.  Brit.  Tenth  edition. 

LIBBY,  WALTER.  An  Introduction  to  the  History  of  Science, 
1917.  A  small  excellently  written  treatise,  general  in 
scope. 

LOCY,  WILLIAM  A.  Article  "  Zoology,"  Cyclopedia  of  Educa- 
tion, 1913.  Also  Biology  and  Its  Makers.  See  list  of 
fifty  books. 


BIBLIOGRAPHY  195 

MEDICINE.  Related  topics,  dealing  with  the  history  of  anat- 
omy, embryology,  physiology,  etc.,  are  treated  in  the 
various  Histories  of  Medicine. 

MERZ.  A  History  of  European  Thought  in  the  Nineteenth 
Century,  vol.  II,  Scientific  Thought,  1903. 

MIALL,  L.  C.  The  Early  Naturalists— Their  Lives  and  Work 
(1530-1789),  1.912.  Good. 

OSBORN,  HENRY  F.  From  the  Greeks  to  Darwin,  1894.  For 
other  references  to  the  history  of  evolution  see  below, 
under  evolution. 

THOMSON,  J.  ARTHUR.  The  Science  of  Life.  See  list  of  fifty 
books. 

WALSH,  J.  J.    The  Popes  and  Science,  1908. 

WHITE,  ANDREW,  J.  A  History  of  the  Warfare  of  Science  with 
Theology  in  Christendom,  2  vols.,  1900.  For  Vesalius 
and  the  overthrow  of  authority  in  science,  etc. 

WILLIAMS,  HENRY  SMITH.  A  History  of  Science,  5  vols., 
1904.  Also  The  Story  of  Nineteenth  Century  Science, 
1900.  Good  portraits. 

(b)  Biography 

General  Reference.  RICHARDSON,  B .  W.  Disciples  of  &scu- 
lapius,  2  vols.,  1901.  Collected  papers  from  the  Ascle- 
piad,  containing  accounts  with  portraits  of  Harvey, 
J.  Hunter,  Malpighi,  Vesalius  and  others. 

Agassiz,  Louis.  Life  and  Correspondence,  by  his  wife,  2 
vols.,  1885.  Life,  Letters  and  Works,  Marcou,  2  vols., 
1896.  " Agassiz  at  Peiukese,"  Amer.  Nat.,  1898.  "What 
we  Owe  to  Agassiz,"  Wilder,  Pop.  Sci.  Mo.,  July,  1907. 

Aristotle.  CUVIER  on,  a  panegyric.  GEORGE  H.  LEWES, 
Aristotle — A  Chapter  from  the  History  of  Science,  1864, 
a  critical  study.  HUXLEY,  On  some  Mistakes  attributed 
to  Aristotle. 


196     THE  MAIN  CURRENTS  OF  ZOOLOGY 

Balfour,  F.  M.  M.  FOSTER,  in  Nature,  vol.  29,  1882.  Also, 
Life  with  portrait  in  the  Memorial  Edition  of  Balfour's 
Works.  OSBORN,  Recollections,  with  portrait,  Science, 
vol.  2,  1883.  WALDEYER,  Archiv  fur  Mikr.  Anat.,  1882. 

Baer,  Karl  E.  von.  Leben  und  Schriften,  his  autobiography, 
1864, 2nd  edition,  1886.  Life  by  STEIDA,  1886.  Obituary, 
Proceed.  Roy.  Soc.  Lond.,  1878.  Nature,  vol.  15,  ELECKEL, 
The  History  of  Creation,  vol.  I,  1884.  LOCY,  "Von  Baer 
and  the  Rise  of  Embryology,"  Pop.  Sci.  Mo.,  1905. 
Rev.  Scient.,  1879.  Fine  portrait,  as  a  young  man,  in 
Harper's  Magazine  for  1899. 

Bernard,  Claude.    Life  by  MICHAEL  FOSTER.    Excellent. 

Bichat,  Francois  X.    The  Practioner,  vol.  56,  1896. 

Bois-Reymond,  Emil  Du.    See  Reymond. 

Boveri,  Theodor.  Sketch  in  Science  by  RICHARD  GOLD- 
SCHMIDT,  Feb.  25,  1915. 

Brooks,  William  K.  CONKLIN,  J.  Hop.  Univ.  Circulars. 
The  Century,  vol.  25.  A  sketch  of  his  life  by  some  of 
his  former  students  and  associates,  three  portraits, 
Jour.  Exp.  Zob'L,  vol.  9,  1910. 

Burdon-Sanderson.  Nature,  vol.  73,  1905-06.  A  memoir, 
Nature,  vol.  89,  1912. 

Cajal,  Ramon  y.    See  Ramon  y  Cajal. 

Cohn,  Ferdinand.  Blatter  der  Erinnerung,  with  portrait, 
1898. 

Cope,  E.  D.  aA  Great  Naturalist,"  H.  F.  OSBORN  in  The 
Century,  vol.  33,  1897.  GILL,  "Edward  Drinker  Cope, 
Naturalist,"  Amer.  Naturalist,  1897.  Sketches  of, 
Amer.  Journ.  Sci.,  vol.  157,  1899.  Nature,  vol.  59, 
1898-99.  Pop.  Sci.  Mo.,  vol.  13,  1878.  Ibid.,  vol.  19, 
1881;  Science,  vol.  9,  1899.  Obituary  Notice,  with  por- 
traits, Amer.  Naturalist,  1897. 

Cuvier,  Georges.    Life  by  FLOURENS.    Memoires  by  MRS. 


BIBLIOGRAPHY  197 

LEE,  1833.  BUCKLE,  History  of  Civilization,  vol.  I, 
pp.  633,  et  seq.  LOCY,  Biology  and  Its  Makers,  Chap- 
ter VII. 

Darwin,  Erasmus.  KRAUSE'S  Life  of  E.  Darwin,  translated 
into  English,  1879.  PACKARD,  Life  of  Lamarck,  chap- 
ter XIV. 

Darwin,  Charles  R.  Life  and  Letters  by  his  Son,  2  vols.,  new 
edition,  1896.  More  Letters  of  Charles  Darwin,  2  vols., 
1903.  Chapter  in  MARSHALL'S  Lectures  on  the  Dar- 
winian Theory.  POULTON,  Charles  Darwin  and  the 
Theory  of  Natural  Selection,  1896.  The  original  com- 
munications of  Darwin  and  Wallace,  with  letter  of 
transmissal  signed  by  Lyell  and  Hooker,  published  in 
the  Trans.  Linnaan  Soc.,  1858,  were  reprinted  in  the 
Pop.  Sci.  Mo.,  Oct.  n,  1912. 

Dohrn,  Anton.  BOVERI  in  Science,  Oct.  n,  1912.  Pop. 
Sci.  Mo.,  vol.  66,  p.  99,  portrait. 

Dujardin,  Felix.  Notice  Biographique  by  JOUBIN,  with 
portraits  and  illustrations,  Archives  de  Parasitol,  vol.  4, 
1901.  Dujardin's  original  description  of  Sarcode,  Ann. 
des  Sci.  Nat.  (Botanique),  vol.  4,  p.  367,  1835. 

Duthiers.    See  Lacaze-Duthiers. 

Edwards.    See  Milne-Edwards. 

Ehrenberg,  Christian  G.  Life  by  LAUE,  1895.  KENT, 
Manual  of  Infusoria,  vol.  I. 

Fabre,  J.  H.  LEGROS,  FABRE,  Poet  of  Science,  1917. 
MAETERLINCK,  in  Introduction  to  Fabre's  Life  of  the 
Spider.  ELEANOR  VAN  HORN,  American  Magazine,  1907. 
Literary  Digest,  1907. 

Foster,  Michael.    Nature,  vol.  75,  1907,  p.  345. 

Galton,  Francis.  Memories  of  my  Life,  1908.  Sketches  of, 
Pop.  Sci.  Mo.,  vol.  29,  1886,  Nature,  vol.  70,  1907. 

Gegenbaur,  Karl.    Erlebtes  und  Erstrebtest,  portrait,  1901. 


198      THE  MAIN  CURRENTS  OF  ZOOLOGY 

Anat.  Anzeiger,  vol.  23,  1903.  Ann.  Rept.  Smithson. 
Inst.,  1904. 

Gesner,  Conrad.  BROOKS  in  Pop.  Sci.  Mo.,  1885,  illustra- 
tions. 

Haeckel,  Ernst.    His  Life  and  Work  by  BOLSCHE,  1906. 

Harvey,  William.  FOSTER,  Lectures  on  the  Hist,  of  Physiol- 
ogy, Lecture  II,  Excellent.  DALTON,  History  of  the  Cir- 
culation. HUXLEY,  William  Harvey,  a  critical  essay.  Life 
by  D'ARCY  POWER,  1898.  BROOKS,  "Harvey  as  Em- 
bryologist,"  Bull.  Johns  Hop.  Hospital,  vol.  8,  1897. 
Good.  MORETON,  An  Anatomical  Dissertation  upon 
the  Movement  of  the  Heart  and  Blood  in  Animals,  a  fac- 
simile reproduction  of  the  first  edition  of  the  famous 
De  Motu  Cordis  et  Sanguinis,  1628,  with  English  transla- 
tion, 1894.  Life  by  WILLIS  in  The  Works  of  Harvey 
rendered  into  English,  Sydenham  Soc.,  1847. 

His,  Wilhelm.  F.  P.  MALL  in  Amer.  Journ.  Anatomy,  vol.  4, 
1905.  Sketch  Anat.  Anzeiger,  vol.  26,  1904. 

Hunter,  John.  The  Scientific  Works  of  J.  Hunter,  2  vols., 
1 86 1 .  RICHARDSON,  Disciples  of  JEsculapius,  vol.  i ,  1 901 . 

Huxley,  T.  H.  Life  and  Letters,  by  his  son,  1901.  Numerous 
Sketches  at  the  tune  of  his  death,  1895.  See  Nature, 
Pop.  Sci.  Mo.,  Nineteenth  Century,  etc. 

Jenner,  Edward.  CAMAC,  Epoch-Making  Contributions  to 
Medicine,  Surgery  and  the  Allied  Sciences,  1909. 

Koch,  Robert.  Pop.  Sci.  Mo.,  vol.  36,  1889.  Review  of  Re- 
views, vol.  2,  1890.  Ann.  Rept.  Smithson.  Inst.,  1911, 
p.  651,  with  portrait.  Sketches  and  references  to  his 
discoveries  numerous. 

Kolliker,  Albrecht  von.  His  Autobiography,  Erinnerungen 
aus  Meinem  Leben,  1899,  several  portraits.  WELDON, 
"Life  and  Works,"  Nature,  vol.  58,  with  fine  portrait. 
STERLING,  Ann.  Rept.  Smithson.  Inst.,  1902. 


BIBLIOGRAPHY  199 

Lacaze-Duthiers,  Henri  de.  Life  with  portraits  in  Archives 
de  Zool.  Experiment,  vol.  10,  1902. 

Lamarck,  H.  B.  A.  S.  PACKARD,  Lamarck,  the  Founder  of 
Evolution,  1901.  The  best  single  reference  on  Lamarck. 

Leidy,  Joseph.  Nature,  vol.  44.  Pop.  Sci.  Mo.,  vol.  28, 
1891.  A  Tribute  by  A.  S.  Minot,  Science,  1913.  His 
University  Career,  by  W.  Hunt,  1892. 

Leuckart,  Rudolph.  Archives  de  ParasitoL,  vol.  i,  no.  2. 
Nature,  1898. 

Leeuwenhoek,  Antony  van.  New  biographical  facts  hi 
RICHARDSON,  Disciples  of  dSsculapius,  vol.  i,  p.  108. 
LOCY,  Pop.  Sci.  Mo.,  April,  1901. 

Leydig,  Franz.  Brief  sketch  in  his  Horae  Zoologicae,  1902. 
Also  in  MIALL  and  DENNEY,  The  Cockroach,  1886. 

Linnaeus,  Carolus.  CADDY,  Through  the  Fields  with  Lin- 
ntzus,  1887.  "Jubilee  at  Upsala,"  Science,  April  26, 
1907.  Many  sketches  and  references  in  periodical  lit- 
erature in  1907 — the  two  hundredth  anniversary  of  his 
birth. 

Lister,  Joseph.  WRENCH,  G.  T.,  Lord  Lister,  His  Life  and 
Work,  1913.  Pop.  Sci.  Mo.,  vol.  52,  1898.  Rev.  of 
Reviews,  vol.  14,  1896.  Celebration  of  Lister's  8oth 
birthday,  Pop.  Sci.  Mo.,  1907. 

Ludwig,  Carl.  BURDON-SANDERSON,  "Ludwig  and  Modern 
Physiology,"  Ann.  Rept.  Smithson.  Inst.,  1896.  LOM- 
BARD, W.  P.,  "  The  Life  and  Work  of  Carl  Ludwig," 
Science,  Sept.  15,  1916. 

Mall,  Franklin  P.  HUBER,  In  Memoriam,  Anat.  Record, 
Jan.  1918;  Flexner,  An  Appreciation,  Sabin,  Scientific 
Achievements,  Science,  March  15,  1918. 

Malpighi,  Marcello.  RICHARDSON,  Vol.  II.  ATTI,  Life  and 
Works,  in  Italian,  1847.  Marcello  Malpighi  e  I'Opera 
Sua,  1897 — a  collection  of  addresses  at  the  unveiling 


200     THE  MAIN  CURRENTS  OF  ZOOLOGY 

of  Malpighi's  statue  at  Crevalcuore,  that  by  Kolliker 
excellent.  LOCY,  "Malpighi,  Swammerdam  and  Leeu- 
wenhoek,"  Pop.  Sci.  Mo.,  1901.  MACCALLUM,  J.  Hop. 
Univ.  Hospit.  Bull. 

Mendel,  Gregor.  BATESON,  W.,  Mendel's  Principles  of 
Heredity,  1902,  also  1904.  Contains  biographical  notice 
and  translation  of  the  original  papers  on  hybridization. 
Ann.  Kept.  Smithson.  Inst.,  1901-1902.  Pop.  Sci.  Mo., 
vol.  62,  1903;  vol.  63,  1904.  Science,  vol.  23,  1903. 

Milne-Edwards,  H.  Biographical  sketch  in  Ann.  Rept. 
Smithson.  Inst.  for  1913. 

Minot,  C.  S.  Notice  by  H,  H.  DONALDSON,  Science,  Dec.  25, 
1914;  by  C.  W.  ELIOT,  Science,  May  14,  1915.  F.  T. 
LEWIS,  with  portrait. 

Montgomery,  Thomas  H.   CONKLIN,  Science,  Aug.  15, 1913. 

Morton,  W.  T.  G.  CAMAC,  Epoch-Making  Contributions  to 
Medicine,  Surgery  and  the  Allied  Sciences,  1909. 

Muller,  Johannes.  VERWORN,  General  Physiology,  1899.  His 
life,  complete  list  of  works,  etc.,  in  Geddchtnissrede  auf 
Johannes  Muller  by  Du  BOIS-REYMOND,  1860.  Eloge, 
in  English,  by  Virchow,  Edinburg.  Med.  Jour.,  vol.  4. 
Picture  of  his  statue  in  Coblenz,  Archivfur  Mikr.  Anat., 
vol.  55. 

Owen,  Richard.  Life  and  Letters,  2  vols.,  1894.  CLARK, 
Old  Friends  at  Cambridge  and  Elsewhere,  pp.  349  et  seq. 

Pasteur,  Louis.  Life  by  RENE  VALLERY-RADOT,  2  vols., 
1894.  Life  by  PERCY  and  G.  FRANKLAND,  1901.  Pasteur 
and  After  Pasteur,  STEPHEN  PAGET,  1914.  "Pasteur  at 
Home,"  illustrated,  TARBELL  in  McClure's  Mag.,  vol.  i, 
1893.  Review  of  VALLERY-RADOT' s  "Life  of  Pasteur," 
McClure's  Mag.,  vol.  19,  1902.  Nature,  vol.  52,  1895. 
Life  by  his  son-in-law,  translated  by  Lady  Hamilton, 
1886.  Sketches  of  Pasteur  very  numerous. 


BIBLIOGRAPHY  201 

Ramon  y  Cajal,  S.  LOCY,  Biology  and  Its  Makers,  portrait, 
p.  176. 

Reaumur,  Rene  A.  Portrait  and  life  in  Les  Savants  Mo- 
dernes,  p.  332.  MIALL,  The  Early  Naturalists,  p.  244, 
1909. 

Reed,  Walter.  H.  A.  KELLEY,  Walter  Reed  and  Yellow  Fever, 
1906. 

Redi,  Francesco.  HUXLEY,  "  Spontaneous  Generation," 
Scientific  Memoirs,  vol.  4,  1901.  Same  article,  British 
Assn.  adv.  Sci.,  1870.  Biographical  sketch,  Archives  de 
ParasitoL,  vol.  i,  1898.  MAB  BIGELOW,  English  transla- 
tion of  Redi's  Esperienze  Intorno  Alia  Generatione  DegV 
Insetti  (1668),  1909. 

Saint-Hilaire,  Geoffroy.  PACKARD'S  Life  of  Lamarck,  chap- 
ter 13. 

Schaudinn,  Fritz  R.   Pop.  Sci.  Mo.,  vol.  70, 1907. 

Schleiden,  M.  Sketch  with  portrait,  Pop.  Sci.  Mo.,  vol.  22, 
1882-1883.  SACHS,  Hist,  of  Botany,  1890.  Translation 
of  his  original  paper  of  1838  (Ueber  Phytogenesis) — Illus- 
trations, Sydenham  Soc.,  1847. 

Schultze,  Max.  Sketch  by  SCHWALBE,  with  portrait,  Archiv. 
fur  Mikr.  Anat.,  vol.  10,  1874. 

Schwann,  Theodor.  Sketch,  Pop.  Sci.  Mo.,  vol.  37,  1000; 
The  Catholic  World,  vol.  71, 1900.  Sa  Vie  et  Ses  Travaux, 
FREDERACQ,  1884.  LANKESTER,  Nature,  vol.  25,  1882. 
Translation  of  his  Microscopical  Researches  of  1839, 
Sydenham  Soc.,  1847. 

Spallanzani,  Lazzaro.  FOSTER,  Lectures  on  the  History  of 
Physiology,  1901.  HUXLEY,  "Spontaneous  Generation," 
Scientific  Memoirs,  vol.  4,  1901.  L'Abbato  Spallanzani, 
by  PAVESI,  1901 — portrait. 

Swammerdam,  Jan.  Life  by  BOERHAAVE  in  Biblia  Natures, 
also  The  Book  of  Nature,  1758.  VON  BAER,  "Johann 


202     THE  MAIN  CURRENTS  OF  ZOOLOGY 

Swammerdam's  Leben  und  Verdienste  um  die  Wissen- 
schaft,"  1864,  in  Reden,  vol.  i,  LOCY,  Pop.  Sci.  Mo., 
April,  1901.  MIALL,  The  Early  Naturalists,  1912,  p.  174. 

Vesalius,  Andreas.  ROTH,  Andreas  Vesalius  Bruxellensis, 
the  edition  of  1892,  the  standard  source  of  knowledge 
of  Vesalius  and  his  times.  FOSTER,  Lectures  on  the  His- 
tory of  Physiology,  Lecture  I.  RICHARDSON,  Disciples 
of  jEsculapius,  vol.  I. 

Virchow,  Rodolph.  Celebration  of  the  yoth  birthday  of 
Virchow,  addresses  by  OSLER,  WELCH  and  others,  J.  Hop. 
Univ.  Circulars,  vol.  XI,  1891.  JACOBI,  Med.  Record, 
N.  Y.,  vol.  XX,  1881.  Ann.  Rept.  Smithson.  Inst.,  1902. 

Wallace,  Alfred  R.  My  Life,  2  vols.,  1905.  Lond.  111. 
News,  1913 — large  portrait. 

Whitman,  C.  O.  DAVENPORT,  "The  Personality,  Heredity 
and  Work  of  Charles  Otis  Whitman,"  Amer.  Naturalist, 
vol.  41,  Jan.  25,  1917. 

Weismann,  August.  Sketch  and  brief  autobiography,  The 
Lamp,  vol.  26,  1903.  CONKLIN,  Science,  Jan.  25,  1915. 

Zittel,  Karl  von.  SCHUCHERT,  Biographical  sketch  with 
portrait,  Ann.  Rept.  Smithson.  Inst.,  1903-1904. 

(2)  MANUALS  AND  TEXT-BOOKS  ON  ZOOLOGY 

(a)  Larger  publications 

HERTWIG,  RICHARD.    A  Manual  of  Zoology.    See  list  of  fifty 

books. 
PARKER,  T.  J.,  and  HASWELL,  W.  A.    A  Text  Book  of  Zoology, 

2  VOls.,  1910. 

THOMSON,  J.  ARTHUR.    Outlines  of  Zoology.    See  list  of  fifty 

books. 
The  Cambridge  Natural  History,  edited  by  S.  F.  HARMER  and 

A.  E.  SHIPLEY,  ten  volumes. 


BIBLIOGRAPHY  203 

A  Treatise  on  Zoology,  edited  by  E.  RAY  LANKESTER,  ten 

volumes,  1909. 
The  Riverside  Natural  History,  edited  by  J.  S.  KINGSLEY,  six 

vols.,  1884-1885.     Also  published  under  the  title  The 

Standard  Natural  Hist. 

BREHM,  A.  G.    Tierleben,  ten  volumes,  1890-1893. 
BRONN,  H.  G.    Klassen  und  Ordnungen  des  Thier-reichs,  17 

vols.,  1880 ,  second  edition  in  progress. 

WEYSSE,  ARTHUR  W.     A  Synoptic  Text-Book  of  Zoology, 

1904. 
JORDAN,  DAVID  S.    A  Manual  of  Vertebrates,  1916.    See  list 

of  fifty  books. 

PRATT,  HENRY  S.    A  Manual  of  Common  Invertebrate  Ani- 
mals, 1916.    See  list  of  fifty  books. 
LEUNIS,  JOHANNES.    Synopsis  der  Thierkunde,  2  vols.,  1883- 

1886. 
HOWES,  G.  B.   Atlas  of  Practical  Zootomy,  1902. 

(b)  Single  volumes  of  medium  size  adapted  for  high  school  and 
college  classes 

BIGELOW,  M.  A.,  and  ANNA  N.   Introduction  to  Biology,  1913. 

Also  Applied  Biology,  1911. 
PEABODY,  JAMES  E.,  and  HUNT,  ARTHUR  E.     Elementary 

Biology,  1912. 
SEDGWICK  and  WILSON.    General  Biology,  1895.    A  classic. 

See  list  of  fifty  books. 

CALKINS,  G.  N.    General  Biology,  1914  and  1917. 
NEEDHAM,  JAMES  G.    General  Biology,  1910. 
MCFARLAND,  JOSEPH.     Biology,  General  and  Medical,  3rd 

edition,  1916. 
HEGNER,  ROBERT  W.   An  Introduction  to  Zoology,  1910.   Also 

College  Zoology,*  191 2.    Practical  Zoology,  1915. 
ABBOTT,  JAMES  F.    General  Biology,  1914. 


204     THE  MAIN  CURRENTS  OF  ZOOLOGY 

GALLOWAY,  T.  W.    Introduction  to  Zoology,  2nd  edition,  1909. 
KELLOGG,  VERNON  L.    Animals  and  Man,  1911. 
JORDAN,  KELLOGG,  and  HEATH.    Animal  Studies,  1900. 
HUXLEY,  T.  H.    The  Crayfish,  1881.    See  list  of  fifty  books. 
MORSE,  E.  S.    A  First  Book  of  Zoology.    An  excellent  simple 

account  of  animals  with  unusually  good  sketches.    Now 

out  of  print. 

PEARSE,  A.  S.    A  Text-Book  of  Zoology,  1917. 
Other  good  single  volumes  by  Davenport,  Dougherty,  Her- 

rick,  Hamaker,  Hunter,  Kellogg,  Linville  and  Kelly, 

Osborn. 

(3)  COMPARATIVE  ANATOMY,  EMBRYOLOGY,  ETC. 

WIEDERSHEIM,  ROBERT.  Comparative  Anatomy  of  Verte- 
brates, translated  by  W.  N.  Parker,  3rd  edition,  1907. 

KINGSLEY,  J.  S.  Comparative  Anatomy  of  Vertebrates,  re- 
vised edition,  1917. 

WILDER,  H.  H.    History  of  the  Human  Body,  1909. 

LANG,  ARNOLD.  Text-Book  of  Comparative  Anatomy  (Inver- 
tebrates) translated  by  H.  M.  and  MATILDA  BERNARD, 
vol.  i,  1892,  vol.  2,  1896. 

REIGHARD,  JACOB,  and  JENNINGS,  H.  S.  Anatomy  of  the 
Cat,  1901. 

(b)  Embryology 

HERTWIG,  OSKAR.  A  Text-Book  of  Embryology,  Man  and 
Mammals,  translated  by  E.  L.  Mark,  1892. 

HERTWIG,  OSKAR,  Editor.  Lehrbuch  der  Vergleichenden  und 
Experimentellen  Entwicklungslehre  der  Wirbeltiere,  6  vols., 
1902-1906. 

KORSCHELT  and  HEIDER.  Text-book  of  Embryology  of  Inverte- 
brates, translated  by  Matilda  Bernard,  edited  by  Martin 
Woodward,  4  vols.,  1899. 


BIBLIOGRAPHY  205 

KELLICOTT,  W.  E.   A  Text-book  of  General  Embryology,  1913. 

Also  Outlines  ofChordate  Development,  1913. 
BAILEY  and  MILLER.    See  list  of  fifty  books. 
BALPOUR,  F.  M.     Comparative  Embryology,  2  vols.,  1880- 

1881. 
FOSTER  and  BALFOUR.    Elements  of  Embryology,  1874  and 

1883. 
KEIBEL,  F.,  and  MALL,  F.  P.   Manual  of  Human  Embryology, 

2  vols.,  1910. 
McMuRRicn,  J.  P.    Development  of  the  Human  Body,  5th 

edition,  1915. 

MINOT,  C.  S.    Human  Embryology,  1892. 
MINOT,  C.  S.    A  Laboratory  Text-Book  of  Embryology,  2nd 

edition,  1910. 
/    McBRiDE,  E.  W.    Text-Book  of  Embryology,  vol.  i,  Inverte- 

brata,  1916. 
PRENTISS,  C.  W.,  and  AREY,  L.  W.   A  Text-book  of  Vertebrate 

Embryology,  1917. 
LILLIE,  FRANK  R.    See  list  of  fifty  books. 

(4)  BOOKS  ON  SPECIAL  TOPICS 
Birds. 

CHAPMAN,  FRANK.    Bird-Life.    See  list  of  fifty  books. 

BARROWS,  WALTER  B.    See  list  of  fifty  books. 

BAIRD,  BREWER  and  RIDGWAY.     Birds  of  North  America, 

1875- 

KNOWLTON,  FRANK  H.    Birds  of  the  World,  1909. 
REED,  CHESTER  A.    Bird  Guide,  Part  I,  Water  Birds,  Game 

Birds  and  Birds  of  Prey.    Part  II,  Land  Birds,  1908. 

Cytology. 

HERTWIG,  OSKAR.    The  Cell,  translated  by  Campbell,  1895. 
v     WILSON,  E.  B.    The  Cell.    See  list  of  fifty  books.    A  classic. 


206      THE  MAIN  CURRENTS  OF  ZOOLOGY 

Genetics  and  Heredity. 

CONKLIN.    Heredity  and  Environment.    See  list  of  fifty  books. 
WALTER.    Genetics.    See  list  of  fifty  books. 
BATESON.    Mendel's  Principles.    See  list  of  fifty  books. 
CASTLE,  W.  E.    Genetics  and  Eugenics,  1916. 
DAVENPORT,  C.  B.   Heredity  in  Relation  to  Eugenics. 
PUNNETT.    Mendelism.    See  list  of  fifty  books. 
WILSON,  JAMES.    A  Manual  of  Mendelism,  1916. 
GUYER,  M.  F.    Being  Well  Born,  1916. 
THOMSON,  J.  ARTHUR.    Heredity,  1908. 

Evolution. 

CLODD,  EDWARD.    Pioneers  of  Evolution,  1897. 

COPE,  E.  D.    Primary  Factors  of  Evolution,  1896. 

DARWIN,  CHARLES.   See  list  of  fifty  books,  and  Biography. 

Fifty  Years  of  Darwinism,  Centennial  Addresses  (n  Ad- 
dresses), 1909. 

JUDD,  JOHN.    The  Coming  of  Evolution.    See  list  of  fifty  books. 

ROMANES,  GEORGE  J.    See  list  of  fifty  books. 

OSBORN,  H.  F.    From  the  Greeks  to  Darwin. 

KELLOGG,  VERNON  L.  Darwinism  To-Day.  See  list  of  fifty 
books. 

LULL,  R.  S.    Organic  Evolution.    See  list  of  fifty  books. 

SCOTT,  W.  B.    The  Theory  of  Organic  Evolution,  1917. 

WEISMANN,  AUGUST.    See  list  of  fifty  books. 

PACKARD,  A.  S.    Lamarck.    See  list  of  fifty  books. 

LAMARCK,  J.  B.  Zoological  Philosophy,  translated  by  Hugh 
Elliot,  1914. 

DRUMMOND,  HENRY.    The  Ascent  of  Man,  1894. 

FISKE,  JOHN.    The  Destiny  of  Man. 

Insects. 

DOANE,  R.  W.    Insects  and  Disease.    1910. 

FOLSOM,  J.  W.    Entomology,  1909. 


BIBLIOGRAPHY  207 

KELLOGG,  VERNON  L.    American  Insects,  1904  and  1908. 
HOWARD,  L.  O.    Mosquitoes,  1901.    Also,  The  Insect  Book, 

1905. 
HOLLAND,  W  G.    The  Butterfly  Book,  1898.    Also,  The  Moth 

Book,  1903. 
REILEY,  WILLIAM  A.,  and  JOHANNSEN,  O.  A.    Handbook  of 

Medical  Entomology,  1915. 
WHEELER,  WILLIAM  M.    Ants,  1910. 

Protozoa. 

BttTSCHLi,  0.     Die  Protozoa  in  Bronn's  Klassen  und  Ord- 

nungen  des  Thier-Reichs,  vol.  i,  3  parts,  1880-1889. 
CALKINS,  G.  N.    The  Protozoa,  1901.   Also  Protozoology,  1909. 
DOFLEIN,  F.    Lehrbuch  der  Protozoenkunde,  3rd  edition,  1911. 
CONN,  H.  W.    A  Preliminary  Report  on  the  Protozoa  of  Fresh 

Water  of  Connecticut,  1905. 
KENT.    Manual  of  the  Infusoria,  3  vols. 
JENNINGS,  H.  S.    Behavior  of  the  Lower  Organisms,  1906. 
LEIDY,  JOSEPH.    Fresh  Water  Rhizopods  of  North  America , 

1879. 

(5)  Miscellaneous 

ADAMS,  C.  C.    Guide  to  the  Study  of  Animal  Ecology,  1913. 

BROOKS,  W.  K.    The  Foundations  of  Zoology,  1898. 

NEEDHAM,  J.  G.,  and  LLOYD,  J.  T.  The  Life  of  Inland  Waters, 
1916. 

WARD,  H.  B.,  and  WHLPPLE,  G.  C.    Fresh-Water  Biology,  1918. 

CASTLE,  CONKLIN,  EAST,  DAVENPORT  and  TOWER.  Heredity 
and  Eugenics,  1912. 

CHILD,  C.  M.    Senescence  and  Rejuvenescence,  1915. 

DRIESCH,  HANS.  The  Science  and  Philosophy  of  the  Or- 
ganism, 1908. 

GASKELL,  WALTER.    The  Origin  of  Vertebrates,  1908. 


208     THE  MAIN  CURRENTS  OF  ZOOLOGY^ 

HEILPRIN,  A.    Geographical  Distribution  of  Animals. 

HERRICK,  FRANCIS  H.  Audubon,  The  Naturalist,  2  vols., 
1917. 

JORDAN,  D.  S.,  and  EVERMANN,  B.  W.  American  Food  and 
Game  Fishes,  1902. 

KEITH,  ARTHUR.    The  Antiquity  of  Man,  1915. 

LUCAS,  F.  A.    Animals  of  the  Past,  1902. 

MORGAN,  T.  H.    Evolution  and  Adaptation,  1903. 

MORGAN,  T.  H.,  and  others.  The  Mechanism  of  Mendelian 
Heredity,  1915. 

OSBORN,  H.  F.    The  Age  of  Mammals,  1910. 

OSBORN,  H.  F.    The  Origin  and  Evolution  of  Life,  1917. 

PATTEN,  WILLIAM.  The  Evolution  of  the  Vertebrates  and  their 
Kin,  1912. 

LANKESTER,  E.  RAY.    The  Kingdom  of  Man,  1907. 

MARSHALL,  C.  E.,  and  others.    Microbiology,  1911. 

MAST,  S.  O.    Light  and  the  Behavior  of  Organisms,  1911. 

METSCHNIKOFF,  ELIE.  Inflammation.  Also,  The  Prolonga- 
tion of  Life. 

NEWMAN,  H.  H.    The  Biology  of  Twins,  1917. 

THOMSON,  J.  ARTHUR.    Darwinism  and  Human  Life,  1911. 

WILLISTON,  S.  W.  Water  Reptiles  of  the  Past  and  Present, 
1914. 

HOWELL,  WILLIAM  H.  A  Text-Book  of  Physiology,  2nd  edi- 
tion, 1908. 

STOHR,  PHILIPP.    Text-book  of  Histology,  1903. 

JORDAN,  H.  E.,  and  FERGUSON,  J.  S.  A  Text-book  of  Histol- 
ogy, 1916. 

EDINGER,  LUDWIG.  The  Anatomy  of  the  Central  Nervous 
System,  translated  by  W.  S.  Hall,  1899.  Several  later 
editions  of  this  valuable  work  in  German. 

BURKHOLDER,  J.  F.    The  Anatomy  of  the  Brain,  1912. 

JOHNSTON,  J.  B.    The  Nervous  System  of  Vertebrates,  1906. 


INDEX 


Acquired  characters,  inheritance 
of,  159;  nature  of,  159;  Weis- 
mann  on,  159 

Adjuncts  to  the  study  of  Zoology, 
123 

Agassiz,  Louis,  at  Penikese,  119; 
biographical  references  to,  195; 
portrait,  118 

Alternative  inheritance,  39 

Amphimixis,  the  source  of  varia- 
tions, 158,  159 

Anaesthetics,  168;  Morton  and 
ether,  168,  170;  and  painless 
surgery,  165, 168;  O.  W.  Holmes 
supplies  the  name,  168 

Ancient  science,  43 

Anellida,  89 

Animal  behavior,  studies  of,  in, 
112 

Animal  kingdom,  the,  84-94;  psy- 
chology and  behavior,  112; 
series,  the,  92 

Animals,  classification  of,  84-93; 
the  number  of,  93;  sub-kingdoms 
or  phyla,  86-93 

Anopheles  mosquito,  the  carrier 
of  malaria,  130 

Antiquity  of  man,  98 

Antiseptic  surgery,  29 

Aristotle,  44;  biographical  refer- 
ences to,  195;  greatest  investi- 
gator of  antiquity,  44;  influence 
of,  45;  portrait,  54 

Arrest  of  inquiry,  effect  of,  45 

Arthropoda,  89,  90 

Artists,  prehistoric,  98 


B 

Bacteria,  and  antiseptic  surgery, 
29;  discovery  of,  25;  disease 
producing,  28 

Bacteriology,  Cohn  and,  26;  Koch, 
26,  33;  Pasteur,  26,  27;  rise  of, 
25-27 

Baer,  Karl  von,  biographical  refer- 
ences to,  196;  and  embryology, 
72;  his  great  classic  on  the  de- 
velopment of  animals,  72;  one 
of  the  ten  foremost  men,  177; 
portrait,  72 

Balfour,  F.  M.,  biographical  refer- 
ences to,  196;  masterly  work 
of,  74;  portrait,  72;  rank  in 
embryology,  73 

Behavior,  animal,  112 

Bernard,  Claude,  biographical  ref- 
erences to,  196;  discoveries,  81; 
in  physiology,  80;  greatest 
physiologist  of  all  time,  184; 
portrait,  72 

Bichat,  and  investigation  of  the 
tissues,  67 

Binomial  nomenclature  of  Lin- 
naeus, 52,  53 

Biographical  references  to  the 
eminent  biologists,  195-202 

Biological  advances,  the  five 
chief,  ii ;  the  outstanding,  10- 
42. 

Biological  laboratories,  118,  119; 
Naples,  118;  Woods  Hole,  etc., 
119 

Biological  progress,  atmosphere 
engendered  by,  186;  continuity 


209 


210 


INDEX 


of,  4;  controversies  produced 
by,  187;  of  the  nineteenth  cen- 
tury, 10 

Biology,  Zoology  the  central  sub- 
ject of,  i,  6 

Books,  a  suggested  library  of 
fifty,  191-193;  lists  of  the  best 
reading,  191-208;  some  useful, 
188-190 

Boveri,  biographical  references  to, 
196;  eminence  in  cytology,  21; 
portrait,  16 

Brooks,  biographical  references  to, 
196 

Brown,  Robert,  discovers  nucleus 
of  plant  cells,  10 

Bruce,  Colonel,  and  sleeping  sick- 
ness, 139;  observations  on  sleep- 
ing sickness,  138-141 

Buff  on,  a  forerunner  of  Lamarck, 
144 

Burdon-Sanderson,  biographical 
reference  to,  196 


Cajal,  Ramon  y,  reference  to  por- 
trait of,  201 

Cell-Theory,  The,  16-22;  an- 
nouncement of,  16;  early  de- 
fects, 19,  20;  formulation  of, 
18;  Modifications  of,  20,  21; 
recent  tendencies,  122;  Schlei- 
den,  17;  Schwann,  17;  Schwann's 
treaties,  18;  modern  statement 
of,  21 

Chemistry,  and  biology,  8 

Chordata,  91 

Chromosomes,  as  bearers  of  hered- 
ity qualities,  42;  discovery  of,  41 

Circulation    of    the    Blood,    78; 


Harvey's  demonstration  of,  78; 
ocular  proof  of,  Leeuwenhoek, 
176;  Malpighi,  176 

Classification  of  Animals,  53,  54; 
tabular  view  of,  60 

Ccelenterata,  87 

Cohn,  biographical  reference  to, 
196;  and  bacteriology,  26 

Comparative  Anatomy,  becomes 
experimental,  114;  rise  of,  62-67; 
recent  tendencies  of,  123 

Continuity  of  the  germ-plasm,  155 

Cope,  E.  D.,  biographical  refer- 
ences to,  196;  a  great  naturalist, 
96;  portrait,  96 

Culture-periods,  of  palaeolithic 
man,  99,  100 

Cuvier,  biographical  references  to, 
196-197;  debate  with  Saint- 
Hilaire,  66;  founder  of  com- 
parative anatomy,  63;  of  struc- 
tural zoology,  62-67;  of  verte- 
brate paleontology,  67,  178; 
one  of  the  ten  foremost  men, 
177;  portrait,  54 

Cytology,,  Boveri  and,  21;  a  de- 
partment of  biology,  21,  122; 
recent  tendencies  of,  122,  123; 
studies  of,  122 


Darwin,  Charles,  biographical  ref- 
erences to,  197;  natural  selec- 
tion, 149,  150;  one  of  the  ten 
foremost  men,  179;  origin  of 
species,  153;  original  draft  of 
his  theory,  154;  parallelism  in 
thought  with  Wallace,  153, 
154;  portrait,  22;  reception  of 
his  theory,  152 


INDEX 


211 


Darwin,  Erasmus,  a  forerunner  of 
Lamarck,  144 

Darwinism,  not  the  same  as  or- 
ganic evolution,  143;  vagueness 
regarding,  143 

De  Vries,  Hugo,  mutation  theory 
of,  159-161;  portrait,  156 

Divisions  of  Zoology,  the  chief, 
106 

Dohrn,  Anton,  biographical  refer- 
ences to,  197;  and  the  Naples 
station,  118 

Dujardin,  Felix,  12,  13;  biographi- 
cal references  to,  197;  discoverer 
of  protoplasm,  12;  portrait,  16; 
sarcode,  13 

E 

Echinodermata,  89 

Ecology,  56,  no 

Economic  Entomology,  117 

Edwards,  Milne-  ,  65 

Eimer,  and  orthogenesis,  162 

Embryology,  70,  108;  Balfour  and, 
73;  chapter  on,  70-76;  impor- 
tance of  in  zoology,  70,  72;  rise 
of,  70-76;  Von  Baer  and,  72 

Embryological  Record,  The,  72 

English,  The,  rank  of  in  biological 
progress,  184,  185 

Entomological  Bureau  at  Wash- 
ington, 118 

Ether,  in  painless  surgery,  165, 
167,  169 


Eugenics,  36,  116;  books  on,  206 
Evolution,    controversies    regard- 
ing, 163,  164;  generalities  con- 
cerning, 143;  the  factors  of,  164; 


mental,  of  animals,  112;  present 
status  of,  163 

Evolution  Theories,  22,  143-164; 
Darwin's  theory,  148-154;  De 
Vries,  159-161;  Lamarck,  found- 
er of,  144;  Weissman,  154-159; 
replacing  theories,  161;  sup- 
porting theories,  161 

Experimental  morphology,  114; 
study  of  heredity,  35;  zoology, 


Fabre,  biographical  references  to, 
197;  the  Hunter- Wasps,  127; 
portrait,  136;  writings  on  in- 
sects, 126 

Factors  of  Evolution,  164 

Fermentation,  28 

Fossil  remains,  chapter  on,  95- 
105;  collections  in  New  Haven, 
97;  hi  New  York,  97;  of  man: — 
Heidelberg  jaw,  103;  Java  skull, 
102;  Neanderthal  skull,  100; 
Piltdown  skull,  103;  prehistoric 
artists,  99;  implements,  98 

Fossil,  bearing  rocks,  thickness  of, 
95;  horses,  96,  97 

Foremost  Men  of  Biological  His- 
tory, the  ten,  174-180 

French,  contributions  to  biological 
progress,  184,  185;  tempera- 
ment, 184 


Galton,  biographical  references 
to,  197;  portrait,  36;  work  on 
inheritance,  36 

Gegenbaur,  65;  biographical  refer- 
ences to,  197 


212 


INDEX 


Gelatine  method  of  Koch,  33 
General  physiology,  as  a  division 

of  zoology,  77-83 
Genetics,  the  science  of,  112,  113 
German,  contributions  to  biologi- 
cal progress,  184, 185;  mentality, 
184 

Germ-Cells,  the,  156 
Germ-Plasm,   continuity  of,   156, 

157 
Germ  theory  of  disease,  24,  26,  29, 

30;  Koch  and,  32,  33;  Pasteur 

and,  26 
Gesner,  50,  51 
Greatest  men  of  biological  history, 

the  ten,  174-180 
Greek  science,  43,  44,  45 


Haller,  74 

Harvey,  49,  78,  127,  128;  bio- 
graphical references  to,  198; 
book  on  the  circulation,  78, 
175;  circulation  of  the  blood, 
78;  in  physiology,  78;  one  of 
the  ten  foremost  men,  175, 
portrait,  156 

Heredity,  experimental  study  of, 
35;  Galton,  36;  Mendel,  37; 
material  basis  of,  41,  42 

Hertwig,  Oskar,  75 

His,  in  embryology,  75,  76 

Histology,  66,  67,  108 

Holmes,  O.  W.,  names  anaesthetics, 
168 

Human  ancestry,  98,  99,  100 

Huxley,  152;  biographical  refer- 
ences to,  198;  portrait,  156 

Hybrids  of  plants,  Mendel,  37 

Hydrophobia,  30 


Inheritance,  alternative,  39;  of 
acquired  characters,  159;  ex- 
perimental study  of,  35;  Galton, 
36;  Mendel,  37-41 

Inoculation,  Pasteur's  methods, 
30,  32;  for  smallpox,  170 

Inquiry,  the  arrest  of,  45 

Insects,  a  chapter  on,  125-142; 
and  disease,  127-142;  and  ferti- 
lization of  flowers,  126;  habits 
of,  126 

Intellectual  progress,  Zoology  and, 
185-187 

Isolation,  a  factor  of  organic 
evolution,  162 


Jardin,  des  plantes,  63;  du  Roi,  63 
Jenner,  and  vaccination,  170-173; 

portrait,  136 
Jennings,   on   behavior   of  lower 

organisms,  112 


Koelliker,  biographical  references 
to,  198;  and  histology,  68;  por- 
trait, 72 

Koch,  Robert,  32,  33;  biographical 
references  to,  198;  and  germ 
theory  of  disease,  32,  33;  por- 
trait, 36 


Laboratories,  marine,  118,  119 
Lacaze-Duthiers,  65;  biographical 

references  to,  199 
Lamarck,   the  founder  of  evolu- 
tion, 144;  of  invertebrate  paleon- 
tology, 67;   biographical  refer- 


INDEX 


213 


ences  to,  199;  influence,  23;  his 
theory  of  evolution,  144-148; 
neo-Lamarackism,  147;  portrait, 
146 

Laveran,  discovers  micro-organism 
of  malaria,  128 

Lazear,  138 

Leidy,  96;  biographical  references 
to,  199;  portrait,  96 

Leuckart,  59;  biographical  refer- 
ence to,  199;  and  classification 
of  animals,  59,  60;  portrait,  54 

Leydig,  69 

Limnology,  121 

Linnaeus,  52,  57,  176;  biographical 
references  to,  199;  and  his  influ- 
ence, 52-57;  one  of  the  ten  fore- 
most men,  176;  portrait,  54; 
his  Systema  Naturae,  53,  56 

Lister,  and  antiseptic  surgery,  29; 
biographical  references  to,  199; 
portrait,  36 

Long,  Crawford,  and  painless 
surgery,  169 

Ludwig,  biographical  reference 
to,  199;  hi  physiology,  184 

Lyell,  influence  on  evolutionary 
thought,  152 

M 

Main  currents  of  zoology,  4,  5, 
9;  pathways  of  zoology,  106- 
120 

Malaria,  parasite  of,  128-134;  pro- 
tection against,  130,  131;  trans- 
mitted by  mosquitoes,  127-135 

Mall,  F.  P.,  biographical  refer- 
ences to,  199;  his  embryological 
collection,  76, 124 

Malpighi,  51;  biographical  refer- 


ences to,  109;  one  of  the  ten 
foremost  men,  176 

Man,  the  antiquity  of,  98;  fossil 
remains  of,  100-105 

Men,  the  ten  foremost  of  biological 
history,  174-180 

Manson,  132 

Marine  zoology,  118,  119;  bio- 
logical stations,  119,  120 

Mendel,  37,  180;  biographical 
references  to,  200;  law  of,  38- 
41;  one  of  the  ten  foremost  men, 
1 80;  portrait,  36;  rank  of,  180 

Mendelism,  40,  41,  113 

Mental  evolution  of  animals,  112 

Micro-organisms,  25,  26,  27 

Micro-parasitology,  27 

Microscopic  observation,  51 

Microscopists,  the  pioneer,  51 

Middle  Ages,  46,  47;  zoology  of 
the,  46 

Minot,  C.  S.,  biographical  refer- 
ences to,  200;  his  embryological 
collection,  124;  influence  on 
biology,  176;  portrait,  96 

Miscellaneous  divisions  of  zoology, 
116 

Mohl,  and  protoplasm,  13 

Mollusca,  90 

Morphology,  experimental,  114; 
and  physiology,  parallel  de- 
velopment of,  77 

Morton,  W.  T.  G.,  biographical 
reference  to,  200;  and  the  dis- 
covery of  anaesthetics,  165, 
167-169;  portrait,  136 

Mosquitoes,  as  disease  carriers, 
131,  132;  transmit  malaria,  130, 
133;  and  yellow  fever,  136 

Miiller,     Johannes,     biographical 


214 


INDEX 


references  to,  200;  in  physiology, 
79;  as  a  teacher,  79,  80;  makes 
physiology  comparative,  80;  one 
of  the  ten  foremost  men,  178; 
portrait,  80 
Mutation,  the  theory  of,  159-161 

N 

Naples,  biological  station  at,  118 

National  contributions  to  biologi- 
cal progress,  181-185 

Nations,  rank  of  in  biological  prog- 
ress, 181-185 

Natural  history,  52,  56,  106 

Nature,  the  oneness  of,  3 

Natural  selection,  theory  of,  149; 
Darwin  and,  149;  illustrations 
of,  150,  151 

Neanderthal  skull,  100 

Nemathelminthes,  88 

Neo-Lamarckism,  147 

Neurology,  122 

Nineteenth  century,  outstanding 
biological  advances  of,  10-42 

Nomenclature  in  zoology,  52,  53 

Nucleus,  discovery  of  in  plants,  10 

Number  of  animals,  93 

O 

Observation,  arrest  of,  45;  the 
method  of  science,  46,  47;  the 
renewal  of,  47 

Oceanography,  120 

Oneness  of  nature,  3 

Organic  evolution,  isolation  a  factor 
of,  162;  present  status  of,  163; 
theories  of,  143-164;  Darwin, 
148;  De  Vries,  159;  Lamarck,  144; 
Weismann,  154;  rival  theories, 
161;  supporting,  or  auxiliary,  161 


Origin  of  species,  153 
Orthogenesis,  162 
Outstanding    biological    advances 
of  the  nineteenth  century,  10-42 


Painless  surgery,  165-170 

Paleontology,  Cuvier  founds  verte- 
brate, 67,  178;  Cope,  and,  96;  a 
division  of,  zoology,  109;  La- 
marck founds  invertebrate,  67; 
Zittel  and,  96 

Parasitology,  117 

Pasteur,  26-32;  biographical  ref- 
erences to,  200;  one  of  the  ten 
foremost  men,  179;  portrait,  28 

Pasteur  Institute,  the,  31 

Path-breakers  of  zoology,  183- 
184 

Pathology,  69 

Philosophical  zoology,  115 

Physical  basis  of  inheritance,  41 

Physiology,  general,  a  division  of 
zoology,  80,  82,  no;  Bernard, 
81,  82,  178;  Harvey,  78;  Miiller, 
79,  178;  rise  of,  78-83 

Phyla  of  animals,  85 

Physiological  method,  83 

Pithecanthropus  erectus,  103 

Platyhelminthes,  88 

Porifera,  87 

Prehistoric,  artists,  99;  man,  98 

Progress  of  science,  a  reconstruc- 
tive force,  1 86 

Protoplasm,  discovery  of,  11-16 

Protozoa,  86 

Protozoology,  116,  117 


Quinine,  use  of  in  malaria,  134 


INDEX 


215 


Rank,  of  Mendel,  1 80;  of  the  na- 
tions in  biological  progress,  181- 
185;  of  Pasteur,  179 

Reading,  comments  on,  188-190; 
lists  of  zoological,  191-208 

Recent  activity  in  zoology/i2i,  122 

Recent  tendencies  of  zoology,  121- 
123 

Redi,  201 

Reed,  Walter,  135;  biographical 
references  to,  201;  portrait,  136; 
and  yellow  fever,  136-138 

Reference  books,  191-208;  a  sug- 
gested library  of  fifty,  191-193; 
and  periodical  articles,  191-208 

References  to  biographical  sketches 
of  biologists,  195-202 


Sarcode,  or  protoplasm,  3 

Schleiden,  17 

Schultze,  Max,  14,  79;  biographical 
references  to,  201;  and  the  cell- 
theory,  20;  one  of  the  ten  fore- 
most men,  179-180;  portrait,  16 

Schwann,  biographical  references 
to,  201;  founder  of  the  cell- 
theory,  1 8;  portrait,  16 

Science,  of  the  ancients,  43;  of 
the  Middle  Ages,  46,  47 

Serum  inoculations,  of  Pasteur,  30 

Siebold,  and  classification  of  ani- 
mals, 58,  60 

Silk-worm,  Malpighi's  monograph, 
176 

Sleeping  Sickness,  138-141,  atoxyl 
in,  141;  Bruce  and,  139;  mode 
of  transmission,  140;  parasite 
of,  139 


Small-Pox,  Jenner  and,  170,  173; 

vaccination  for,  170 
Species,    early    views    regarding, 

146;  fixity  of,  146;  the  origin  of, 

147,  i53 
Spencer,    Herbert,    and    organic 

evolution,  152 
Spontaneous  generation,  28 
Structural  zoology,  107 
Study  of  types,  93 
Swammerdam,  Jan,  51 
Systema  Naturae,  of  Linnaeus,  53, 56 
Systematic  zoology,  109 


.Ten  foremost  men  of  biological 
history,  174-181 

Tsetse-fly,  transmits  sleeping  sick- 
ness, 141 

Theory,  the  cell,  16-22;  of  organic 
evolution,  22;  the  protoplasm, 
14,  15.  Theories  of  organic 
evolution,  143-164;  Darwin, 
148;  De  Vries,  159;  Lamarck, 
144;  Weismann,  154;  other 
theories,  161-163 

Toxins  and  antitoxins,  30 

Trypanosome,  the  parasite  of 
sleeping  sickness,  139,  140 

Types  of  animals,  the  study  of,  93 


Vaccinination,  for  small-pox,  Jen- 
ner and,  170-173;  Pasteur,  30 

Variation  of  animals,  one  of  the 
factors  of  evolution,  164 

Vertebra ta,  91 

Vesalius,  biographical  references 
to,  202;  and  reform  of  anatomy, 
48,  49,  176 


216 


INDEX 


Virchow,  69;  biographical  refer- 
ences to,  202 

Virus,  137 

Vries,  Hugo,  de,  159-160;  muta- 
tion theory  of,  160;  portrait,  156 

W 

Wallace,  A.  R.,  and  Darwin,  153, 

154 

Weismann,  154;  biographical  ref- 
erences to,  202;  a  nee-Darwin- 
ian, 154;  portrait,  156;  his 
theory  of  heredity,  154,  155; 
of  evolution,  156,  outstanding 
features  of,  159 

Whitman,  C.  O.,  biographical 
references  to,  202;  influence  on 
biology,  119;  portrait,  96 


Yellow  Fever,  cause  of,  135;  the 
Commission  of,  136;  trans- 
mitted by  mosquitoes,  137; 
Walter  Weed  and,  136 


Zittel,  and  paleontology,  96 

Zoology,  adjuncts  to  the  study  of, 
123;  aspects  of,  3,  5;  a  subject 
of  general  education,  1-8;  as  a 
unified  science,  iv,  2;  basal  to 
the  study  of  medicine,  7;  books 
about,  191-208;  the  central 
subject  of  biology,  i,  6;  emerges, 
43-51;  experimental,  113;  the 
foremost  men  of,  174-180;  of 
fossil  remains,  95-105;  greatest 
present  activity  in,  121,  122; 
and  intellectual  progress,  185- 
187;  the  maul  currents  of,  4,  5, 
9;  main  pathways  of,  106-120; 
miscellaneous  divisions  of,  116; 
philosophical,  115;  its  position 
in  biology,  6;  recent  tendencies 
of,  121-123;  structural,  147 

Zoological  Progress,  a  system  of 
thought,  iii 

Zoological  Thought,  continuity 
of,  4 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


e-  •  -.. 

JUM  5  1943 

APR  5    J966 

MAR  3  01966 

LD  21-5m-l,'39(7053s7) 

UNIVERSITY  OF  CALIFORNIA  LIBRARY 


